|ENGINE MANAGEMENT SYSTEM|
|ENGINE MANAGEMENT SYSTEM - MPi MEMS 1.9 MGF until VIN 522572||CONNECTOR No C0159|
|ENGINE MANAGEMENT SYSTEM - VVC MEMS 2||Check Tom's site for VVC data|
|ENGINE MANAGEMENT SYSTEM - MPi/VVC MEMS 3 MGF since VIN 522573, MGF Trophy, MGTF|
The Modular Engine Management System Version 3 (MEMS 3) is a sequential, multipoint fuel injection system controlled by the Engine Control Module (ECM).
The ECM uses the components shown in the control diagram to control the operation of the:
- Fuel system
- Ignition system
- Variable Valve Control (VVC) system (where applicable)
- Evaporative Emissions (EVAP) system
- Engine cooling fan (s)
- Air Conditioning (A/C) (where applicable)
- Steptronic Electro Mechanical Constantly Variable Transmission (EM-CVT) (where applicable)
The ECM uses the speed/density method of air flow measurement to calculate fuel delivery. This method calculates the density of intake air by measuring its pressure and temperature. The density signal, combined with the engine speed signal, allows the ECM to make a calculation of the air volume being inducted and determine the quantity of fuel to be injected to give the correct air/fuel ratio.
Engine Control Module (ECM)
The ECM is located on a bracket on the rear bulkhead in the engine compartment. Two harness connectors are used to connect the ECM to the main harness. The ECM electronic components are housed in an aluminium case for heat dissipation and protection from electro-magnetic interference. The ECM is connected to earth via pins 59, 66 and 73. With the ignition off, the ECM is supplied with battery voltage to power the memory. The voltage is supplied from the battery positive terminal via the under bonnet fusebox fuse 2 to pin 80 of the ECM. When the ignition switch is in position II (ignition on), the ECM also receives battery voltage, via the passenger compartment fusebox fuse 14, at pin 61. The ECM energises the main relay by completing the earth path for the relay coil which is connected to the ECM at pin 54. The main relay provides battery voltage to various peripheral components and also to the ECM at pin 19. When the ignition switch is turned to position II, the ECM primes the fuel system by running the fuel pump for approximately two seconds. This is achieved by completing the earth path for the fuel pump relay coil. The fuel pump relay coil is connected to battery voltage at the ignition switch, the earth being supplied by the ECM at pin 68. The ECM references the sensors and the IAC valve stepper motor prior to start up. Security code information is exchanged between the ECM and the alarm ECU via a wire connected between pin 72 of the ECM and the alarm ECU. When the ignition is turned to position III (crank,) the ECM communicates with the alarm ECU. If it receives authority to start, the ECM begins ignition and fuelling when CKP and CMP sensor signals are detected. The ECM will run the fuel pump continuously when CKP sensor signals are received (crank turning). When the ignition switch is turned to position 0 (off), the ECM switches off ignition and fuelling to stop the engine. The ECM continues to hold the main relay in the on position until it has completed the power down functions. Power down functions include engine cooling and referencing the IAC valve stepper motor and includes memorising data required for the next start up. When the power down process is completed, the ECM switches off the main relay and enters a low power mode. During low power mode the ECM will consume less than 1mA. If the ECM suffers an internal failure, such as a break down of the processor or driver circuits, there are no back up systems or limp home capability. If a sensor circuit fails to supply an input, this will result in a substitute or default value being adopted where possible. This enables the vehicle to function, but with reduced performance.
Heated Oxygen Sensor (H02S)
A H02S is located upstream of the catalytic converter, in the exhaust manifold (up to 2001 MY) or the twin pipe section of the exhaust front pipe (from 2001 MY). From 2001 MY, a HO2S is also installed in the downstream side of the catalytic converter. The upstream HO2S provides a feedback signal to the ECM to enable closed loop fuelling control. Where fitted, the downstream HO2S provides a feedback signal to enable the ECM to monitor the efficiency of the catalytic converter, by comparing the signals from the upstream and
downstream HO2S. If the upstream H02S fails, the ECM adopts an open loop fuelling strategy. If the downstream HO2S fails, the ECM suspends catalytic converter monitoring.
A. Ambient Air.
B. Exhaust Gases.
1. Protective ceramic coating.
3. Zirconium Oxide.
CAUTION: H02 sensors are easily damaged by dropping, excessive heat or contamination. Care must be taken not to damage the sensor housing or tip.
- The H02S becomes very hot, take care when working near it.
- Do not measure the resistance of the sensing element.
- Observe the correct torque tightening value when installing the H02S.
- Do not subject the H02S to mechanical shocks.
- The H02S may be contaminated if fuel with added lead is used.
The HO2S consists of a sensing element, the outer surface of which is exposed to exhaust gases, whilst the inner surface is exposed to ambient air. The sensor has a ceramic coating to protect the sensing element from contamination and heat damage. The amount of oxygen in ambient air is constant at approximately 20%. The oxygen content of the exhaust gases varies with the AFR with a typical value for exhaust gas of around 2%. The difference in oxygen content of the two gases produces an electrical potential difference across the sensing element. Rich mixtures, which burn almost all of the available oxygen, produce high sensor
voltages. During lean running, there is an excess of oxygen in the mixture and some of this oxygen leaves the combustion chamber unburnt. In these conditions, there is less difference between the oxygen content of the exhaust gas and the ambient air, and a low potential difference (voltage) is output by the HO2S.
d.H02S Output in mV.
The material used in the sensing element only becomes active at a temperature of 300 °C (572 °F), therefore it is necessary to provide additional heating via an electrical resistive element. The element uses a 12V supply provided by the ECM and allows a short warm up time and minimises emissions from start-up. The resistance of the heating element can be measured using a multimeter and should be 6 Ohm at 20 °C (68 °F).
Crankshaft Position (CKP) Sensor
The variable reluctance CKP sensor is mounted at the rear of the engine with the sensor tip facing the engine face of the flywheel and is secured in the casting with a single screw. The sensor tip of the CKP sensor is adjacent to a profiled target ring formed on the inner face of the flywheel. The signal produced by the CKP sensor allows the ECM to calculate the rotational speed and angular position of the crankshaft. This information is required by the ECM to calculate ignition timing, fuel injection timing and fuel quantity during all conditions when the engine is cranking or running. If the CKP sensor signal is missing, the vehicle will not run as there is no substitute signal or default. The CKP sensor is variable reluctance sensor and provides an analogue voltage output to the ECM relative to the speed and position of the target on the flywheel. A permanent magnet inside the sensor applies a magnetic flux to a sensing coil winding. This creates an output voltage which is read by the ECM. As the gaps between the poles of the target pass the sensor tip, the magnetic flux is interrupted and this causes a change to the output voltage (e.m.f.). It is important to note that the ECM is unable to determine the exact position of the engine with its four stroke cycle from the CKP sensor alone: the CMP sensor must also be referenced to provide sufficient data for ignition control and sequential injection. The "spaces" on the target are spaced at a rate of one hole per 10°. There are only 32 holes, this leaves four "spaces" where a single hole is missing. When the crankshaft is positioned at TDC (cylinder number one firing position) the CKP sensor is positioned at 55°BTDC. The "missing" holes are positioned at 80°, 110°, 260°and 300°before the CKP sensor position.
Camshaft Position (CMP) Sensor
The CMP sensor provides a signal which enables the ECM to determine the position of the camshaft relative to the crankshaft. This allows the ECM to synchronise fuel injection and, on VVC engines, monitor valve timing.
CMP Sensor - MPi Engines
The CMP sensor on MPi engines is located on the camshaft cover (under the plastic cover) at the opposite end to the camshaft drive and reads off a reluctor on the exhaust camshaft. The sensor is a hall effect sensor which detects the reluctor mounted on the exhaust camshaft. The sensor receives a battery supply from the main relay. The sensor operates on the principle of a voltage generated when the sensor is exposed to a magnetic flux. This causes a potential difference in voltage as the reluctor passes the sensor which is detected as a digital signal by the ECM.
CMP Sensor - VVC Engines
The CMP sensor on VVC engines is located on the rear face of the cylinder head and reads off a reluctor on the inlet camshaft. The CMP sensor is a variable reluctance sensor which does not require a power supply. The sensor consists of a permanent magnet and a sensing coil winding. The signal is generated by changes which occur in the magnetic flux of the magnet. As the reluctor passes the sensor, an electromotive force (e.m.f.) is generated in the coil winding. The amplitude of the e.m.f. is proportional to the frequency of the change of magnetic flux which is detected by the ECM as an analogue signal.
CMP Reluctor - MPi and VVC Engines
The reluctor consists of a single "tooth" design which extends over 180°of the camshaft"s rotation, for this reason it is known as a half moon cam wheel. The half moon cam wheel reluctor enables the ECM
to provide sequential fuel injection at start up, but it cannot provide a back-up signal in cases of CKP sensor failure. If the CMP sensor signal is missing, the engine will still start and run, but the fuel injection may be out of phase. This will be noticeable by a reduction in performance and driveability, together with an increase in fuel consumption and emissions. As the camshaft rotates the signal will switch between the high and low voltages. The position of the half moon cam wheel relative to the camshaft is not adjustable. The air gap between the CMP sensor tip and the half moon cam wheel is not adjustable.
Manifold Absolute Pressure (MAP) Sensor
The output signal from the MAP sensor, together with the CKP and IAT sensors, is used by the ECM to calculate the amount of air induced into the cylinders. This enables the ECM to determine ignition timing and fuel injection duration values. The MAP sensor receives a 5V ±4% supply voltage from the ECM and provides the ECM with an analogue signal which relates to the absolute manifold pressure and allows the ECM to calculate engine load. If the MAP signal is missing, the ECM will substitute a default manifold pressure reading based on crankshaft speed and throttle angle. The engine will continue to run with reduced driveability and increased emissions, although this may not be immediately apparent to the driver. The ECM will store fault codes which can be retrieved using TestBook.
Engine Coolant Temperature (ECT) Sensor
The ECT sensor is located in the cooling system outlet elbow from the cylinder head and provides a signal to the ECM which allows the engine temperature to be determined. The ECT sensor consists of an encapsulated negative temperature coefficient (NTC) thermistor which is in contact with the engine coolant. The ECM uses engine temperature to calculate fuelling and ignition timing parameters during start up. It is
also used to provide a temperature correction for fuelling and ignition timing when the engine is warming up, running normally or overheating. The ECT signal is used by the ECM to control the engine cooling fans.
If the ECT sensor fails or becomes disconnected, the ECM will use a default value which is based on values from the engine oil temperature sensor. The driver may not notice that a fault is present although a fault code will be stored in the ECM which can be retrieved using TestBook. The default value will also include operation of the cooling fans in fast mode when the engine is running.
Intake Air Temperature (IAT) Sensor
The IAT sensor is located in the intake manifold near cylinder number four fuel injector. The sensor consists of an NTC thermistor mounted in an open housing to allow air flow over the sensing element. The IAT sensor provides a signal which enables the ECM to adjust ignition timing and fuelling quantity according to the intake air temperature, thus ensuring optimum performance, driveability and low emissions. The IAT sensor is part of a voltage divider circuit which consists of a regulated 5 volt supply, and a fixed resistor (both are inside the ECM) and a temperature dependent variable resistor (the IAT sensor). The IAT sensor operates in a similar manner to the ECT sensor. Refer to ECT sensor diagram and description for method of IAT sensor operation. If the IAT sensor fails, or is disconnected, the vehicle will continue to run. The ECM will substitute a default value using the information from the speed/load map to run the engine, but adaptive fuelling will be disabled. This condition would not be immediately apparent to the driver, but the ECM will store fault codes which can be retrieved using TestBook.
Engine Oil Temperature Sensor
The engine oil temperature sensor is located in the oil filter housing on MPi engines and in the Hydraulic Control Unit (HCU) on VVC engines. The sensor provides a signal which allows the ECM to adjust fuelling values according to engine oil temperature, to produce optimum engine performance and minimum emissions during the engine warm up phase. On VVC engines, the ECM also uses the oil temperature to derive the viscosity of the oil passing through the HCU, which indicates how quickly the VVC mechanism will respond. The engine oil temperature sensor consists of an encapsulated Negative Temperature Coefficient (NTC) thermistor which is in contact with the engine oil. The engine oil temperature sensor operates in a similar manner to the ECT sensor. If the engine oil temperature sensor fails, the ECM will substitute a default value which is ramped up 80°C (176°F). This condition will not be apparent to the driver, with the exception of the temperature gauge which will display incorrect readings depending on the sensor failure.
The vehicle will run but may suffer from reduced engine performance and increased emissions as adaptive fuelling is disabled. The ECM will store fault codes which can be retrieved using TestBook.
Throttle Position (TP) Sensor
The TP sensor is mounted on the throttle body and is driven from the end of the throttle spindle. The TP sensor consists of a potentiometer which provides Idle Air Control (IAC) Valve an analogue voltage that the ECM converts to throttle position information. The TP sensor signal is required for the following vehicle functions:
- Idle speed control
- Throttle damping
- Deceleration fuel cut off
- Engine load calculations
- Acceleration enrichment
- Full load enrichment
- Automatic gearbox shift points.
The TP sensor is a potentiometer which acts as a voltage divider in an external ECM circuit. The potentiometer consists of a 4kOhm +- 20% resistive track and a wiper arm, driven by the throttle spindle,
which sweeps over the track. The track receives a regulated 5 V ±4% supply from the ECM, together with an earth path. As the wiper arm moves over the track it will connect to areas of different voltage ranging from 0 to 5 volts. The "output " from the wiper arm is connected to the ECM to provide an analogue voltage signal. The TP sensor requires no adjustment as the ECM will learn the lower voltage limit which correspond to
closed throttle. If the TP sensor signal is missing the vehicle will continue to run but may suffer from poor idle control and throttle response. The ECM will store fault codes which can be retrieved using TestBook.
through a duct which leads from the inlet manifold to a pipe connected to the throttle body. The bobbins are connected to the ECM driver circuits. Each of the four connections can be connected to 12 volts or earth, enabling four "phases" to be obtained. The ECM drives the four phases to obtain the desired idle speed. When the ignition is switched off the ECM enters a power down routine which includes "referencing" the stepper motor. This means that the ECM will rotate the motor so that it can memorise the position when it next needs to start the engine.
The IAC valve is located on the inlet manifold. It allows the ECM to control the engine idling speed by regulating the amount of air which by-passes the throttle valve. It also allows the ECM to provide a damping function when the throttle is closed under deceleration, this reduces hydrocarbon (HC) emissions. The IAC valve is controlled by the ECM using a stepper motor. This consists of a core which is rotated by magnetic fields produced by two
The stepper motor controls the volume of air passing
The stepper motor referencing procedure can take from three to five seconds. If the ECM cannot reference the stepper motor during power down, it will do so at ignition on. If the stepper motor fails, there are no back up idle control systems. The idle speed may be too high or too low and if a load is placed on the engine it may stall. The ECM will store fault codes which can be retrieved by TestBook.
Two ignition coils are mounted on the camshaft cover above the spark plugs for cylinders 1 and 3 and secured with screws. Each coil operates a pair of spark plugs using the wasted spark principle. The coil has a plug connection on its lower face and an ht lead which connects to the second plug. The coil fitted above cylinder 1 is attached to the spark plug for cylinder 1 and the ht lead connects to the spark plug for cylinder 4. The coil fitted above cylinder 3 is attached to the spark plug for cylinder 3 and the ht lead connects to the spark plug for cylinder 2.
WARNING: The ht voltage of the ignition system is in excess of 50 kV and the lt voltage is in excess of 400 volts. Voltages this high can cause serious injury and may even be fatal. Never touch any ignition components while the engine is running or being cranked.
CAUTION: Never crank or run the engine with the ht leads disconnected from the ignition coils; failure of the ECM and/or the coil will result. Always disable the ignition system by disconnecting the lt connectors from the coil.
Each ignition coil consists of a pair of windings wrapped around a laminated iron core. The primary winding has a resistance of 0.7 Ohm
The fuel injectors are located directly under the fuel rail and connect to the intake manifold runners. Each injector delivers fuel to the engine in a targeted, atomised spray (onto the intake valve heads) which takes place once per cycle. Each injector opens during the intake stroke of the cylinder it supplies. An injector consists of a pintle type needle and seat, and a solenoid winding which lifts the needle against a return spring. The injector nozzle delivers the fuel spray to precise areas of the intake ports to maximise the benefits of the swirl and turbulence in the manifold and head ports.
The solenoid winding has a resistance of 13 - 16 Ohm at 20 deg
The fuel injectors operate at a regulator is located on the end of the fuel rail and excess fuel is returned to the swirl pot via a return line to the tank. The injectors receive fuel under pressure from the fuel rail and a 12 volts supply from the main relay. To deliver fuel to the engine, the ECM has to lift the needle off the injector seat by energising the solenoid. To energise the solenoid the ECM supplies an earth path to the injector winding. If an injector fails, the engine may lose power and driveability. The ECM will store fault codes which can be retrieved using TestBook.
Evaporative Emissions (EVAP) Cannister Purge Valve
The EVAP cannister purge valve is located in the engine compartment on the rear bulkhead. The purge valve is connected via a flexible pipe to the inlet manifold.
The cannister purge valve consists of a solenoid operated valve which is controlled by the ECM using a 12 volts PWM signal. The EVAP cannister purge valve controls the flow of fuel vapours from the EVAP cannister to the intake manifold of the engine. When the vehicle is being driven the ECM will purge the EVAP cannister by opening the cannister purge valve, this allows the vacuum present in the intake manifold to draw fuel vapour from the cannister into the cylinders for combustion. When fuel vapour is being removed from the cannister, fresh air is allowed to enter via an automatic one-way valve, this makes the cannister ready for the next "absorption " phase. The amount of fuel vapour which enters the cylinders can affect the overall AFR, therefore the ECM must only open the cannister purge valve when it is able to compensate by reducing fuel injector duration. The cannister purge valve will only operate under the following conditions:
- Engine at normal operating temperature
- Adaptive fuelling enabled
- Closed loop fuelling enabled.
The alternator is located on a bracket which is attached to the cylinder block on the front RH side of the engine. The alternator is driven by a Polyvee belt from the crankshaft pulley. The alternator converts mechanical energy into electrical energy to power the electrical systems and maintain the battery charge.
The alternator outputs a signal to the ECM which represents the electrical load on the vehicle systems and the mechanical load exerted on the engine by the alternator. The signal output from the alternator is a variable PWM signal which is proportional to the load applied to the engine. The ECM uses the load signal to provide idle speed compensation and to reduce engine speed fluctuations. If the load signal fails, the ECM uses a default value and stores a fault code which can be retrieved using TestBook.
Air Conditioning (A/C) Trinary Switch
The A/C trinary switch is located on the receiver/drier at the rear of the under bonnet compartment. It contains three pressure switches; high, low and medium. The medium switch completes an earth path between the ECM and an earth header joint. The high and low switches are connected between the A/C switch and the ECM. The trinary switch has three functions:
1. To disengage the A/C compressor clutch if the refrigerant pressure falls below the "minimum" specified value.
2. To disengage the A/C compressor clutch if the refrigerant pressure exceeds the "maximum" specified value.
3. To switch the cooling fan to high speed if the refrigerant pressure exceeds the "high" specified value.
A/C Trinary Switch Pressure Settings
Switch Opening Pressure bar (lbf/in 2 ) Closing Pressure bar (lbf/in 2 )
Low 1.96 (28) pressure decreasing 2.35 (34) pressure increasing
Medium 13.7 (198) pressure decreasing 18.6 (270) pressure increasing
High 28.4 (412) pressure increasing 22.6 (328) pressure decreasing Functions 1 and 2 are performed by a single series circuit containing both minimum and maximum pressure switches. The switches are both normally closed, so if either threshold is exceeded the continuity of the earth path to the ECM is broken. This causes the ECM strategy to disengage the A/C compressor clutch on safety grounds. Function 3 is performed by a separate circuit containing a single normally open pressure switch. This switch opens when the pressure exceeds a specified value indicating that extra cooling is required to reduce refrigerant pressure. this will cause the ECM to energise the condenser fan relay
and start the fan.
VVC Mechanism Control (Where Applicable)
Hydraulic Control Solenoid
The ECM controls two solenoids in order to control the VVC mechanism. Only one solenoid will be energised at a time to either drive the VVC mechanism towards minimum cam period, or towards maximum cam period. The desired cam period is calculated by the ECM using engine speed and manifold pressure (engine load). The current cam period is measured by the ECM using the camshaft position sensor. The ECM then energises the correct solenoid in order to move the mechanism towards the desired position.
If the ECM detects any faults with cam period measurement during start up and initial running, the ECM will try and drive the mechanism to minimum cam period. If the ECM loses the cam period signal during
running, the cam period will remain frozen at the last valid period. Engine speed may be limited as low as 5500 rpm depending on cam period when the fault occurred. The engine idle speed will be raised and
will remain raised for the rest of the journey.
Steptronic (EM-CVT) Gearbox (Where Applicable)
The MEMS 3 ECM controls the EM-CVT unit in conjunction with the Gearbox Interface Unit (GIU) and several peripheral gearbox switches and sensors.
The GIU outputs gear selector lever position status, manual/sport selection and snow mode selection to the ECM. The ECM then provides an output to the instrument pack to display the appropriate gear position information in the LCD or illuminate the snow mode or gearbox fault warning lamps. For further information on EM-CVT (Steptronic) gearbox See AUTOMATIC GEARBOX - "EM-CVT",
Description and operation.
Gearbox Interface Unit (GIU)
Electronic control of the EM-CVT Steptronic gearbox operates as an integral part of the MEMS 3 system software. The ECM accepts inputs from the GIU, communicates with the GIU for gearbox control, accepts driver inputs for gear selection and communicates information to the driver via the instrument pack.
The GIU connection which supplies information to the ECM is a serial communication link. This supplies the ECM with all the driver inputs from the gearbox switches.
The ECM output to the GIU is a hardwired connection which instructs the GIU of the required ratio control motor position. This information is output in the form of 500 Hz PWM signals.
Gearbox Shaft Speed Sensor
The ECM receives an input from the EM-CVT gearbox differential speed sensor which is located at the rear of the gearbox. The sensor is a Hall effect sensor which reads off the differential crown wheel teeth to provide a road speed signal. This signal is used by the ECM to determine when the vehicle is stationary and to allow accurate calculation of the true gearbox ratio.
The park/neutral switch is located at the rear of the gearbox and is operated by a cam which moves via a cable with the gear shift selector lever position. An output from the park/neutral switch is connected to the ECM to enable gearbox load compensation. The ECM will adjust the IAC valve stepper motor to the appropriate position to maintain the idle speed when the gearbox is moved into and out of drive or reverse.
The park/neutral switch also operates the reverse lamps via a hardwired connection and controls a shift interlock solenoid which is fitted in selected markets only.
Ignition Switch Signal
A hardwired digital input to ECM pin 61 provides an ignition on signal. When the ECM has been idle for a period of time, it goes into "sleep" (power saving) mode.
When the ECM receives an ignition on signal from the ignition switch, the ECM "wakes up" and energises the main relay.
The main relay is located in the engine management relay module which is positioned behind the ECM mounting bracket. The relay module contains the main relay, the fuel pump relay and the starter relay.
The relay is normally open when the ignition is off. When the ignition is switched on to position II, the ECM provides an earth path for the relay coil which energises, closing the contacts. A permanent battery supply is provided to the relay contacts from fuse 2 in the under bonnet fusebox.
The relay supplies battery voltage to the following components:
- ECM pin 19
- CMP sensor
- Purge valve
- Fuel injectors
- Ignition coils
- Gearbox Interface Unit (GIU) via an in-line 10A fuse.
If the main relay fails, power will not be supplied to the above components and the engine will not start.
The ECM will store fault codes which can be retrieved using TestBook.
Fuel Pump Relay
The fuel pump relay is located in the engine management relay module which is positioned behind the ECM mounting bracket. The relay is normally open when the ignition is off. When the ignition is switched on to position II, the ECM provides an earth path for the relay coil. With the ignition on the relay receives a feed, via the ignition switch, from fuse 14 in the passenger compartment fusebox which energises the relay coil,
closing the contacts. A permanent battery supply is provided to the relay contacts from fuse 2 in the under bonnet fusebox, via the inertia switch. The feed passes through the relay contacts and operates the fuel pump to pressurise the fuel system. The relay will be energised for a short time only to pressurise the fuel system.
When the ignition switch is moved to the crank position III, the ECM will energise the relay when the engine starts cranking and will remain energised until the engine stops. If the engine stalls and the ECM stops receiving a signal from the CKP sensor, the ECM will remove the earth path for the relay, stopping the fuel pump.
WARNING: ALWAYS check for fuel leaks and the integrity of the fuel system before resetting the inertia switch. The inertia switch, when tripped, cuts off the power supply to the relay contacts, disabling the fuel pump in the event of a sudden deceleration. If the fuel pump fails to operate, check that the inertia switch is not tripped. The switch is reset by depressing the rubber cap on the top of the switch. If the fuel pump relay fails, power will not be supplied to the fuel pump and the engine will not start or will stop if already running due to fuel starvation. The ECM will store fault codes which can be retrieved using TestBook.
A/C Compressor Clutch Relay (Where Applicable)
On vehicles fitted with air conditioning, an A/C relay module is located under the bonnet adjacent to the under bonnet fusebox. When the engine is running and the driver requests A/C on, the ECM receives a signal from the A/C switch to pin 56. If conditions are correct, the ECM grants the A/C request by completing an earth path from pin 54 to the A/C clutch relay coil. The A/C clutch relay coil receives a battery feed from the ignition switch position II. The feed is supplied via fuse 15 in the passenger compartment fusebox to the relay coil. The coil will energise closing the relay contacts. A permanent battery supply, via fuse 5 in the under bonnet fusebox, passes through the relay contacts and operates the compressor clutch.
The ECM will disengage the A/C compressor clutch if the coolant temperature exceeds 118°C (244°F) and will re-engage the A/C compressor clutch when the coolant temperature falls to less than 114°C (237°F). If the A/C clutch relay fails, the A/C will be inoperative and the ECM will store fault codes which can be retrieved using TestBook.
The cooling system comprises an engine coolant cooling fan which is located behind the radiator and an engine bay cooling fan located in the engine bay.
On vehicles fitted with A/C, an additional cooling fan is located behind the radiator and A/C condenser. An engine bay cooling fan is located in the engine bay. The fan is used to reduce engine bay temperatures especially when the vehicle is stationary. The fan draws air through the RH air intake into the engine bay. On all vehicles the engine bay cooling fan relay is located adjacent to the passenger compartment fusebox. On vehicles without A/C, the engine cooling fan relay is located behind the under bonnet fusebox. On vehicles with A/C, the engine cooling fan relay and the condenser fan relay are located in the A/C relay module which is located adjacent to the under bonnet fusebox.
Engine Coolant Cooling Fan
The engine cooling fan relay is energised by the ECM on receipt of an appropriate coolant temperature signal from the ECT sensor. When the engine is running, the ECM will energise the relay to operate the fan at a coolant temperature of 104°C (219°F) and will go off when the coolant temperature decreases to less than 98°C (208°F). When A/C is fitted, the engine cooling fan and the condenser fan can operate at two speeds, being operated in series or parallel by the ECM. Refer to the Air Conditioning section for condenser fan details.
Engine Bay Cooling Fan
The engine bay cooling fan relay is energised by the ECM on receipt of an appropriate engine bay temperature signal from the ambient air temperature sensor.
When the engine is running, the ECM will energise the relay to operate the fan when an engine bay temperature of 75°C (167°F) is reached. The ECM has a timer which energises the relay for a
predetermined period. If the temperature decreases to less than 60°C (140°F) before the timer has expired, the ECM will de-energise the relay.
If the engine bay temperature exceeds 130°C (266°F), the ECM will illuminate the engine bay overheat warning lamp in the instrument pack. The warning lamp informs the driver that the engine bay temperature is abnormally high or that a system fault has occurred. When the engine bay temperature falls below 110°C( 230°F) the ECM will extinguish the warning lamp. When the engine is off, the fan remains active for a
predetermined period after the engine is switched off.
Ambient Air Temperature (AAT) Sensor (Engine Bay)
The AAT sensor is located in the engine bay on the header panel directly above the inlet manifold. The AAT sensor receives a supply from ECM pin 21 and is connected to ECM pin 34 which is a common
earth. The AAT sensor operates the engine bay cooling fan as described in Cooling Fans. If the AAT sensor fails, the engine bay cooling fan will operate at all times when the ignition is on and the engine bay overheat warning lamp in the instrument pack will be illuminated.
Engine Bay Cooling Fan Relay
The engine bay cooling fan relay is located adjacent to the passenger compartment fusebox and is the central relay in a block of three. The relay coil and contacts receive a permanent battery feed from fusible link 3 in the under bonnet fusebox and fuse 6 in the passenger compartment fusebox. The relay coil is connected to ECM pin 74 which provides an earth path when cooling fan operation is required. If the cooling fan relay fails, the cooling fan will not operate and engine bay overheat may occur. The ECM will store fault codes which can be retrieved using TestBook.
Engine Bay Overheat Warning Lamp
The engine bay overheat warning lamp is located in the centre warning lamp cluster in the instrument pack. If the engine bay temperature exceeds 130°C (275°F), the ECM will illuminate the warning lamp to inform the driver that the engine bay temperature is abnormally high. When the engine bay temperature falls below 110°C( 230°F) the ECM will extinguish the warning lamp.
The ECM will also illuminate the warning lamp if a cooling fan, relay or AAT sensor fault is detected. The warning lamp receives a feed from the ignition switch when the switch is in position II. When the ECM requires the warning lamp to be illuminated, it completes an earth path from the warning lamp to ECM pin 62.
The ECM provides an output signal on pin 55 for engine speed, derived from the CKP sensor. The signal is passed to the instrument pack for tachometer operation and is also used by the EPAS ECU pin 15 for an engine speed signal. Failure of this output will be shown by the tachometer not functioning. The ECM will record fault codes which can be retrieved using TestBook.
The vehicle immobilisation system operates by the alarm ECU transmitting a unique code to the ECM when the ignition is switched on. If the code is recognised by the ECM it will energise the injectors and allow the engine to start. If no code is received or the code is incorrect, the ECM will disable the vehicle by not energising the fuel injectors.
The alarm ECU also controls the starter relay and will passively disarm the starter relay when the key is removed from the ignition switch. Rearming is performed by turning the ignition on which activates a coil around the ignition key barrel. The coil transmits a waveform signal which excites the remote handset to transmit a re-mobilisation signal. When the signal is received by the alarm ECU, the starter relay will be enabled. Replacement ECM"s are supplied blank and must learn the alarm ECU security code for the vehicle to which it is fitted. When the ECM is connected to the vehicle, TestBook is required to enable the ECM to learn the alarm ECU code. If a new alarm ECU is fitted, the ECM will need to learn the new security code using TestBook.
Rough Road Detection
MEMS 3 has a misfire detection facility which is part of the On-Board Diagnostics (OBD) system. Misfire detection is disabled when the ECM senses that the vehicle is on a "rough road". The system software can detect variations in the signal output and disable misfire detection to prevent incorrect faults being logged by the ECM. The "rough road" signal is passed from the ABS ECU on a hardwired output to the ECM pin 78. The signal is in the form of a square wave digital pulse train of between 0 and 5 V at 8000 pulses per mile. On vehicles without ABS, an ABS reluctor ring is fitted to the LH rear wheel and provides 48 pulses per rotation of the wheel to a variable reluctance sensor. The output from the sensor is received by the GIU which passes a buffered version of the signal to the ECM pin 78.
The electric fuel pump is located inside the fuel tank and is energised by the ECM via the fuel pump relay in the engine management relay module and the inertia switch. The fuel pump delivers more fuel than the maximum load requirement for the engine, maintaining pressure in the fuel system under all conditions.
Fuel Pressure Regulator
The fuel pressure regulator is a mechanical device mounted on the end of the fuel rail. Pressure is controlled by diaphragm spring pressure and is modified by a vacuum signal from the inlet manifold. The regulator ensures that fuel pressure is maintained at a constant pressure difference to that in the inlet manifold. As manifold depression increases, the regulated fuel pressure is reduced in direct proportion. When pressure exceeds the regulator setting, excess fuel is returned to the fuel tank swirl pot which contains the fuel pump pick-up.
Inertia Fuel Cut-Off Switch
The electrical circuit for the fuel pump incorporates an inertia switch which, in the event of a sudden deceleration, breaks the circuit to the fuel pump preventing fuel being delivered to the engine. The switch is located adjacent to the ECM and can be reset by pressing the rubber top.
WARNING: ALWAYS check for fuel leaks and the integrity of the fuel system connections before resetting the switch.
A diagnostic socket allows the exchange of information between the ECM and TestBook or a diagnostic tool using Keyword 2000 protocol. The diagnostic socket is located in the passenger compartment fusebox which is located below the fascia on the driver"s side.
A dedicated diagnostic (ISO 9141 K Line) bus is connected between the ECM and the diagnostic socket and allows the retrieval of diagnostic information and the programming of certain functions using TestBook. The ECM uses a "P" code diagnostic strategy and can record faults relating to the engine management and EM-CVT gearbox interface unit functions.
The "P" codes are qualified by one of the following failure types:
- Min - the minimum expected value has been exceeded
- Max - the maximum expected value has been exceeded
- Signal - the signal is not present
- Plaus - an implausible condition has been detected
From 2001 MY, after detecting a fault which causes an increase of emissions above the legislated threshold, in addition to storing a "P" code the ECM also illuminates a Malfunction Indicator Lamp (MIL) in the instrument pack. The ECM performs a 2 seconds bulb check of the MIL each time the ignition is switched on.
Malfunction Indicator Lamp
ENGINE MANAGEMENT SYSTEM - MEMS
When the throttle pedal is depressed, the ECM receives a rising voltage from the TP sensor and detects a rise in manifold pressure from the MAP sensor. The ECM provides additional fuel by increasing the normal injector pulse width and also provides a number of extra additional pulses on rapid throttle openings.
Over-Run Fuel Cut-Off
The ECM implements over-run fuel cut-off when the engine speed is above 1600 rpm with the engine at normal operating temperature and the TP sensor in the closed position, i.e. when ECM senses that the vehicle is "coasting" with the throttle pedal released. The ECM indexes the IAC valve open slightly to increase the air flow through the engine to maintain a constant manifold depression to keep emissions low. Fuel is immediately reinstated if the throttle is opened. If the engine speed drops below 1600 rpm on over-run, fuel is progressively reinstated.
Over-Speed Fuel Cut-Off
To prevent damage at high engine speeds the ECM will implement fuel cut-off at engine speeds above approximately 7000 rpm. Fuel is reinstated as the engine speed falls.
Ignition Switch Off
In the first 10 seconds after the ignition is switched off, the ECM drives the IAC valve to its power down position (ready for the next engine start), and stores any required information. The ECM then monitors the engine bay temperature using the ambient air temperature sensor. If the temperature is above a certain limit, the ECM will drive the engine bay fan for 8 minutes, and will then power down. If the engine bay temperature is below the limit the ECM will power down after 10 seconds.
The ECM controls fuel quantity by providing sequential injection to the cylinder head intake ports. Sequential injection allows each injector to deliver a precise amount of fuel to the cylinder intake ports, during the induction stroke, in cylinder firing order. The CMP sensor and reluctor allows the ECM to synchronise injection at cranking speed for starting. The precise quantity of fuel delivered is controlled by adjusting the duration of the injector open time. To achieve optimum performance the ECM is able to "learn" the individual characteristics of an engine and adapt the fuelling strategy to suit. This capability is known as adaptive fuel strategy. Adaptive fuel strategy must be maintained under all throttle positions except:
- Cold start
- Hot start
- Wide open throttle.
All of the above throttle positions are deemed to be "open loop". Open loop fuelling does not rely on information from the HO2S, but sets the air/fuel ratio (AFR) according to the stored data in the ECM. During a cold start, the ECM references the ECT sensor to calculate the appropriate amount of fuel required to support combustion and adjusts the idle speed to the correct "fast idle" value. This strategy is maintained until the HO2S is hot enough to provide an accurate feedback signal. The specific nature of the other open loop conditions means that the HO2S feedback is unsuitable as a control value for fuelling. Adaptive strategy also allows the ECM to compensate for wear in engine components and allow for production tolerances in mass produced components such as sensors. To calculate the amount of fuel to be injected into each cylinder, the ECM has to determine the quantity of oxygen available in the cylinder to burn it. This can be calculated by processing information from the following sensors:
- MAP sensor
- CKP sensor
- ECT sensor
- TP sensor.
During one engine revolution, 2 of the 4 cylinders draw in air. The ECM uses the CKP sensor signal to determine the potential air intake volume in the cylinders. The oxygen content of the air contained in the cylinders can be calculated by the ECM using information from the MAP sensor and the IAT sensor. The pressure of the air in the intake manifold will vary according to the following factors:
- The position of the throttle valve (driver input)
- The atmospheric pressure (altitude and weather conditions)
- The mechanical condition of the engine (volumetric efficiency).
The pressure in the intake manifold, downstream of the throttle valve, indicates how much air has flowed into the cylinders. This will decrease at higher altitudes as the air becomes "thinner" or less dense. This will also mean that there will be less oxygen contained in the air which will be available for combustion of fuel. The temperature of the air will also affect the oxygen content. Air which is cool has molecules packed closer together than hot air, therefore; cooler air contains more oxygen for any given volume than hotter air. From the above information, the ECM can calculate how much air has been induced into the cylinders. By comparing these values to a fuelling map stored in the ECM memory, the amount of oxygen induced into the cylinders can be calculated. The values obtained from the ECT sensor, engine oil temperature sensor and TP sensor provide "fine tuning" to the calculations. To deliver the fuel the ECM completes an earth path to the injector coil, opening the injector for the precise amount of time required for the quantity determined. The correct cylinder order is determined by referencing the CMP sensor during start up to synchronise the CMP sensor signal to the CKP sensor signal. The fuel is injected into the inlet ports of the intake manifold and is drawn into the cylinder as an air and fuel mixture. The ECM ensures that the amount of fuel injected is not affected by the variations in inlet manifold pressure. The ECM corrects the injector duration time, using MAP sensor information. The ECM references battery voltage to adjust opening times to suit the state of battery charge. This is required because low battery voltage will mean slower response from the injectors, and could give a leaner AFR than intended.
The ignition timing is an important part of the ECM adaptive strategy. The ignition system consists of two double ended coils, mounted on the cam cover directly over the spark plugs, which operate using the wasted spark principle. Each coil is connected to a pair of spark plugs, 1 and 4, 2 and 3. The spark plugs are connected in series with the secondary winding of the coil so a spark occurs in both cylinders at the same time. When a spark occurs in the cylinder which is on the compression stroke the air/fuel charge is ignited. The spark has no effect on the cylinder at the end of the exhaust stroke, hence the term "wasted" spark. The major advantage of this system is that a distributor cap and rotor arm are eliminated thereby improving performance and reliability. The timing of the spark will affect the quality of combustion and the power produced. The ECM will reference all relevant sensors to achieve the optimum timing for any given condition. This electronically increases the primary coil charging time (dwell angle) as engine speed increases to maintain coil ht voltage at high engine speeds. The ECM calculates ignition timing using inputs from the following:
- CKP sensor
- TP sensor
- ECT sensor
- IAT sensor.
The ECM calculates dwell angle using inputs from the following:
- CKP sensor
- Battery voltage.
At start up the ECM sets ignition timing by referencing the ECT sensor. After start up, the ignition timing will be controlled according to maps stored in the memory and modified according to additional sensor inputs. The choice of ignition point is critical in maintaining engine power output with low emissions. Advancing the ignition may increase power output under certain conditions, but it also increases the amount of oxides of nitrogen (NOx) and carbon monoxide (CO) produced in the combustion chamber. There is a narrow range of ignition points for all engine conditions which give an acceptable compromise between power output and emission control. The ignition mapping contained within the ECM memory keeps the ignition timing within this narrow band. The ignition timing is used to control engine idle speed in conjunction with the IAC valve stepper motor. As the MEMS 3 system does not have a knock sensor, ignition timing advance is controlled using different mapping at high engine and intake air temperatures in order to avoid detonation (pinking).
Idle Speed Control
The ECM regulates the engine speed at idling. The ECM uses two methods of idle speed control:
- Ignition timing adjustment
- IAC valve stepper motor.
When the engine idle speed fluctuates, and there are no additional loads on the engine, the ECM will vary the ignition timing and the IAC valve to regulate the idle speed. This allows very rapid correction of out of tolerance idle speeds. When an additional load is placed on the engine, such as when the power steering is turned on full lock, the ECM uses the IAC valve stepper motor to control the idle speed to specification. The idle speed is determined from the CKP sensor, but there are also inputs to the ECM from the following:
- Park/Neutral switch (EM-CVT)
- A/C system
- Cooling fan status.
If the ECM receives information from the above inputs that an extra load is being placed on the engine, it can immediately compensate and avoid engine poor idle or stall conditions. The IAC valve stepper motor is mounted on the inlet manifold and controls a throttle valve air by-pass port. To increase the idle speed, the stepper motor allows more air to by-pass the throttle and enter the cylinders. To decrease the idle speed, the stepper motor allows less air to enter the cylinders. The stepper motor is a bi-polar type which consists of two windings controlled by pulse width modulated (PWM) signals from the ECM. The position of the stepper motor is always referenced on power down of the ECM, this may take from three to five seconds. The stepper motor is also used to reduce manifold vacuum during deceleration to control emissions.
Evaporative Emissions (EVAP) Control System
The hydrocarbon vapour given off by petrol is harmful to health and the environment. Legislation limits the amount of hydrocarbons (HC) which can be emitted to atmosphere by a motor vehicle. To meet the limits imposed, a charcoal cannister is fitted to the fuel system to absorb fuel vapour from the tank when the vehicle is not in use. The charcoal cannister has a finite capacity and therefore needs to be purged when the vehicle is driven. This is achieved by drawing the fuel vapours out of the cannister and into the cylinders of the engine. The HC vapours are converted into carbon dioxide (CO2) and water (H20) by the combustion process and catalytic converter.
AIR INTAKE SYSTEM - MPi/VVC MEMS 3
1. Air cleaner element
2. Throttle disc
3. IAC valve
4. Inlet manifold
6. Evaporative emission cannister purge valve
7. Evaporative emission cannister
Intake air is drawn into the throttle housing through the air filter element. Incorporated in the throttle housing is the throttle disc and the TP sensor. Air passes from the throttle housing via the manifold chamber into the inlet tracts. Fuel is sprayed into the inlet manifold by the injectors and the air/fuel mixture is drawn into the combustion chamber. Inlet manifold depression is measured by the MAP sensor which is mounted near the end of the inlet manifold chamber. A signal from the MAP sensor is used by the ECM to calculate the amount of fuel to be delivered by the injectors.
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