Engine Management Systems

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BOSCH ME 7.2 ENGINE MANAGEMENTBOSCH ME 7.2 ENGINE MANAGEMENTIntroductionThe Bosch ME 7.2 engine management system (EMS) is similar to the Bosch 5.2.1 systemused in previous Land Rover V8 engines. The main difference between the two systems is the“drive by wire” capabilities of the ME 7.2 EMS.Another main difference between the 5.2.1 system and the ME 7.2 system is that ME 7.2 usesthe Keyword protocol 2000* (KWP2000*) which is an ISO 91414 K line compatible version ofthe Key Word 2000 protocol.Engine Management Component Location, Sheet 1 of 21ECM5Mass Air Flow/Inlet Air Temperature (MAF/IAT) sensor2Variable Camshaft Control (VCC) solenoid6Crankshaft Position (CKP) sensor3Knock sensor (x4)7Electric throttle4Heated thermostat8Main relayBosch ME 7.2 ENGINE MANAGEMENT171

BOSCH ME 7.2 ENGINE MANAGEMENTEngine Management Component Location, Sheet 2 of 243215141361211789710M18 07971721Radiator outlet temperature sensor8Instrument pack2Engine Coolant Temperature (ECT)sensor9Diagnostic socket3Ignition coil10Accelerator Pedal Position (APP)sensor4Injector11Camshaft Position (CMP) sensor5Spark plug12E-box temperature sensor6Purge valve13EAT ECU7Oxygen sensors14E-box

BOSCH ME 7.2 ENGINE MANAGEMENTEngine Management Control Diagram, Sheet 1 of 221543226217201981891716151410121113DAJM18 0805AAHardwired connections7ABS modulator/ECU16Vacuum vent valveDCAN bus8Diagnostic socket17SAI pump relayJDiagnostic ISO 9141 K line busEAT ECU18ECM1APP sensor10Electric cooling fan19LH bank VCC solenoid2Instrument pack11Starter motor20RH bank VCC solenoid3Radiator outlet temperature sensor12Immobilisation ECU21Brake light switch4Ignition warning lamp13HO2S (x 4)22Cruise control switches5Steering angle sensor14Comfort start relay6Alternator15SAI pumpIntroduction9173

BOSCH ME 7.2 ENGINE MANAGEMENTEngine Management Control Diagram, Sheet 2 of 23214205196717188916101514121113AM18 0825AA Hardwired connection7Crankshaft Position (CKP) sensor14Ignition coil1MAF/IAT sensor8Fuse 2515Tank leakage detection module2Camshaft sensorMain relay16Electric throttle3Immobilisation ECU10Ignition switch17Radiator outlet temperature sensor4Injector11Fuel pump18ECM5Auxiliary cooling fan relay12Ignition coil relay19Electrical heated thermostat6Purge valve13Fuel pump relay20Knock sensors1749

BOSCH ME 7.2 ENGINE MANAGEMENTKey FunctionsThe key functions of the Bosch ME 7.2 engine management system are: To control the amount of fuel supplied to each cylinderTo calculate and control the exact point of fuel injectionTo calculate and control the exact point of ignition in each cylinderTo optimize adjustment of the injection timing and ignition timing to deliver the maximumengine performance throughout all engine speed and load conditionsTo calculate and maintain the desired air/fuel ratio, to ensure the 3 way catalysts operate attheir maximum efficiencyTo maintain full idle speed control of the engineTo ensure the vehicle adheres to the emission standards (set at the time of homologation)To ensure the vehicle meets with the fault handling requirements, as detailed in the European On-Board Diagnostic (EOBD) III legislationTo provide an interface with other electrical systems on the vehicleTo facilitate the drive by wire functionsTo control the Variable Camshaft Control (VCC).To deliver these key functions, the Bosch ME 7.2 Engine Control Module (ECM) relies upon anumber of inputs and controls a number of outputs. As with all electronic control units, the ECMneeds information regarding the current operating conditions of the engine and other relatedsystems before it can make calculations, which determine the appropriate outputs. A ControllerArea Network (CAN) bus is used to exchange information between the ECM and the ElectronicAutomatic Transmission (EAT) ECUECMThe ECM is located in the Environmental (E) box, in the front right corner of the enginecompartment. The E-box provides a protective environment for the ECM and is cooled by anelectric fan. The main relay for the ECM is also located in the E-box.Key Functions175

BOSCH ME 7.2 ENGINE MANAGEMENTE-Box1Fuse block4ECM2Cooling fan5E Box temperature sensor3Main relay6EAT ECUA separate temperature sensor is used to monitor E-box temperature and provides a path toearth to control the electric fan. The sensor turns the fan on when the E-box temperaturereaches 35 C (95 F) and turns the fan off when the temperature drops below 35 C (95 F). TheE-box fan draws air in from the passenger compartment, into the E-box and vents back into thepassenger compartment. The fan is also driven for a short period on engine crank,independently of temperature. This is done to ensure the correct function of the fan.176

BOSCH ME 7.2 ENGINE MANAGEMENTThe ECM is programmed during manufacture by writing the program and the engine tune into aFlash Electronic Erasable Programmable Read Only Memory (EEPROM). The EEPROM canbe reprogrammed in service using TestBook/T4. In certain circumstances, it is possible to alterthe tune or functionality of the ECM using this process.Advanced fault monitoring is incorporated into the ECM. It can detect the type and severity offaults, store relevant engine operating conditions (environmental and freeze frame data) andtime that a fault occurs, suspend the operation of some functions and replace the inputs fromfaulty sensors with default values. Environmental data is stored for each fault detected, andconsists of the inputs from three engine sensors, with the inputs stored depending on the fault.The ECM also records additional data in connection with each fault, as follows: The number of occurrences If the fault is currently present If the fault is historic, the number of drive cycles that have elapsed since the fault lastoccurred The time the fault occurred. Time is incremented in hours, hour 0 being the first time theECM is powered-up, hour 1 being 60 minutes of ignition 'on' time, etc.OBD freeze frame data is only stored for emissions related faults. Only one set of freeze framedata can be stored at any one time. Faults are prioritized according to their likely impact onexhaust gas emissions. If more than one emissions related fault occurs, freeze frame data isstored for the fault with the highest priority. Freeze frame data consists of the following: Engine speedEngine loadShort term fuelling trim of LH and RH cylinder banksLong term fuelling trim of LH and RH cylinder banksFuelling status of LH and RH cylinder banksEngine coolant temperatureRoad speed.Fault information is stored in a volatile Random Access Memory (RAM) in the ECM, so will bedeleted if a power failure or battery disconnection occurs.Five electrical connectors provide the interface between the ECM and the engine/vehicle wiring.The five connectors interlock with each other when installed in the ECM. Adjacent connectorsshould be disconnected in turn. The installation sequence is the reverse of removal. Eachconnector groups associated pins together.ECM177

BOSCH ME 7.2 ENGINE MANAGEMENTSystem InputsThe ECM optimizes engine performance by interpreting signals from numerous vehicle sensorsand other inputs. Some of these signals are produced by the actions of the driver, some aresupplied by sensors located on and around the engine and some are supplied by other vehiclesystems. The inputs are as follows: Ignition switchAPP sensorThrottle position feedbackCrankshaft Position (CKP) sensorCruise control signal (from steering wheel switch pack)Brake light switchCamshaft Position (CMP) sensorsEngine Coolant Temperature (ECT) sensorKnock sensorsMass Air Flow/Intake Air Temperature (MAF/IAT) sensorHeated Oxygen Sensors (HO2S)Immobilisation signal (from immobilisation ECU)Fuel level signal (via CAN)Vehicle speed signal (from ABS ECU)Radiator outlet temperatureInternal ambient barometric pressure sensor (altitude sensor)Electronic Automatic Transmission (EAT) information.Electric Throttle SystemThe EMS incorporates an electric throttle control system. This system consists of three maincomponents: Electronic throttle control valve APP sensor ECM.When the accelerator pedal is depressed the APP sensor provides a change in the monitoredsignals. The ECM compares this against an electronic “map” and moves the electronic throttlevalve via a pulse width modulated control signal which is in proportion to the APP angle signal.The system is required to: Regulate the calculated intake air load based on the accelerator pedal sensor input signalsand programmed mapping Monitor the drivers input request for cruise control operation Automatically position the electronic throttle for accurate cruise control Perform all dynamic stability control throttle control interventions Monitor and carry out maximum engine and road speed cut out.178

BOSCH ME 7.2 ENGINE MANAGEMENTAccelerator Pedal Position (APP) Sensor1Detente mechanism5Cables2Sensor spigot6Bush3Pedal7Drum4Springs8APP sensorThe APP sensor is located in a plastic housing which is integral with the throttle pedal. Thehousing is injection moulded and provides location for the APP sensor. The sensor is mountedexternally on the housing and is secured with two Torx screws. The external body of the sensorhas a six pin connector which accepts a connector on the vehicle wiring harness.The sensor has a spigot which protrudes into the housing and provides the pivot point for thepedal mechanism. The spigot has a slot which allows for a pin, which is attached to the sensorpotentiometers, to rotate through approximately 90 , which relates to pedal movement. Thepedal is connected via a link to a drum, which engages with the sensor pin, changing the linearmovement of the pedal into rotary movement of the drum. The drum has two steel cablesattached to it. The cables are secured to two tension springs which are secured in the oppositeend of the housing. The springs provide 'feel' on the pedal movement and require an effort fromthe driver similar to that of a cable controlled throttle. A detente mechanism is located at theforward end of the housing and is operated by a ball located on the drum. At near maximumthrottle pedal movement, the ball contacts the detente mechanism. A spring in the mechanismis compressed and gives the driver the feeling of depressing a 'kickdown' switch when full pedaltravel is achieved.Electric Throttle System179

BOSCH ME 7.2 ENGINE MANAGEMENTAPP Sensor Output GraphAVoltageBAPP sensor angleCKickdown angleThe APP sensor has two potentiometer tracks which each receive a 5V input voltage from theECM. Track 1 provides an output of 0.5V with the pedal at rest and 2.0V at 100% full throttle.Track 2 provides an output of 0.5V with the pedal at rest and 4.5V at 100% full throttle. Thesignals from the two tracks are used by the ECM to determine fuelling for engine operation andalso by the ECM and the EAT ECU to initiate a kickdown request for the automatictransmission.The ECM monitors the outputs from each of the potentiometer tracks and can determine theposition, rate of change and direction of movement of the throttle pedal. The 'closed throttle'position signal is used by the ECM to initiate idle speed control and also overrun fuel cut-off.180

BOSCH ME 7.2 ENGINE MANAGEMENTElectric ThrottleElectric Throttle Control ValveThe Electric Throttle control valve is controlled by the APP sensor via the ECM. The throttlevalve plate is positioned by gear reduction DC motor drive. The DC motor is controlled by aproportionally switched high/low PWM signals at a basic frequency of 2000 Hz. Engine idlespeed control is a function of the Electric Throttle control valve, therefore a separate idle controlvalve is not required.The electric throttle control valve throttle plate position is monitored by two integratedpotentiometers. The potentiometers provide DC voltage feedback signals to the ECM for throttleand idle control functions.Potentiometer one is used as a the primary signal, potentiometer two is used as a plausibilitycheck through the total range of throttle plate movement.If the ECM detects a plausibility error between Pot 1 and Pot 2 it will calculate the inducted airmass from the air mass (from the air mass sensor) and only utilize the potentiometer signalwhich closely matches the detected intake air mass. It does this to provide a fail-safe operationby using a 'virtual' potentiometer as a comparative source.If the ECM cannot calculate a plausible value from the monitored potentiometers (1 and 2) thethrottle motor is switched off and the fuel injection cut out is activated.The electric throttle control valve is continuously monitored during operation. It is also brieflyactivated when the ignition switch is initially turned to position II. This is done to check thevalves mechanical integrity by monitoring the motor control amperage and the reaction speed ofthe feedback potentiometers.Should the electronic throttle need replacing the adaption values of the previous unit will needto be cleared from the ECM. This is achieved by the following process: Using TestBook/T4 clear the adaption values Switch the ignition “OFF” for 10 seconds Switch the ignition “ON”, for approximately 30 seconds the electric throttle control valve isbriefly activated allowing the ECM to learn the new componentElectric Throttle System181

BOSCH ME 7.2 ENGINE MANAGEMENTThis procedure is also necessary after the ECM has been replaced. However the adaptionvalues do not require clearing since they have not yet been established.Crankshaft Position (CKP) SensorThe CKP sensor is located in the transmission bell housing adjacent to the edge of the flexplateflywheel. The sensor reacts to a toothed reluctor ring incorporated into the flexplate to ascertainengine speed and position information. The sensor is located on a split spacer and is secured inposition by two tube spacers and nuts. The split spacer is 18 mm thick on vehicles fitted withautomatic transmission. The thickness of the split spacer determines how far the sensorprotrudes through the cylinder block and, therefore, sets the position of the sensor in relation tothe reluctor ring. The sensor and the spacer are covered by a protective heat shield. The sensorhas three wires attached to it; two signal wires and a screen. The sensor earth screen isconnected to chassis earth through the ECM.CKP SensorThe CKP sensor is an inductive type sensor which produces a sinusoidal output voltage signal.This voltage is induced by the proximity of the moving reluctor ring, which excites the magneticflux around the tip of the sensor when each tooth passes. This output voltage will increase inmagnitude and frequency as the engine speed rises and the speed at which the teeth on thereluctor ring pass the sensor increases. The signal voltage will peak at approximately 6.5 volts ifconnected to the ECM (further increases in engine speed will not result in greater magnitude).The ECM neither specifically monitors nor reacts to the output voltage (unless it is very small orvery large), instead it measures the time intervals between each pulse (i.e. signal frequency).The signal is determined by the number of teeth passing the sensor, and the speed at whichthey pass. The reluctor ring has 58 teeth spaced at 6 intervals, with two teeth missing to givethe ECM a synchronisation point.182

BOSCH ME 7.2 ENGINE MANAGEMENTThe signal produced by the CKP sensor is critical to engine running. There is no back-upstrategy for this sensor and failure of the signal will result in the engine stalling and/or failing tostart. If the sensor fails when the engine is running, then the engine will stall, a fault code will bestored and details captured of the battery voltage, engine coolant temperature and intake airtemperature at the time of the failure. If the signal fails when the engine is cranking, then theengine will not start and no fault will be stored, as the ECM will not detect that an attempt hadbeen made to start the engine. In both cases the tachometer will also cease to functionimmediately and the MIL lamp will be permanently illuminated.During the power-down procedure, which occurs when the ignition is switched off, the ECMstores details of the position of the CKP and CMP sensors. This enables the ECM to operatethe injectors in the correct sequence immediately the engine cranks, to produce a quick enginestart, which serves to reduce emissions when the engine is cold.Camshaft Position (CMP) SensorThere are two CMP sensors which are located on the upper timing case covers. The CMPsensors monitor the position of the camshafts to establish ignition timing order, fuel injectiontriggering and for accurate Variable Camshaft Control (VCC) camshaft advance-retard timingfeedback. The CMP sensor is a Hall-effect sensor which switches a battery fed supply on andoff. The supply is switched when the teeth machined onto the camshaft gear pass by the tip ofthe sensor. The four teeth are of differing shapes, so the ECM can determine the exact positionof the camshaft at any time.CMP SensorUnlike an inductive type sensor, a Hall-effect sensor does not produce a sinusoidal outputvoltage (sine wave). Instead it produces a square wave output. The wave edges are very sharp,giving the ECM a defined edge on which to base its calculations.An implausible signal from the CMP sensor will result in the following: The MIL lamp illuminated after debouncing the fault Loss of performance, due to the corrective ignition strategy being disabled. A default ignition map is used which retards the timing to a safe position Injector operation possibly 360 out of phase, i.e. fuel injected during exhaust stroke ratherElectric Throttle System183

BOSCH ME 7.2 ENGINE MANAGEMENTthan during compression stroke Quick crank/cam synchronisation on start-up feature disabled Some Oxygen sensor diagnostics disabled.In addition, the ECM will store a relevant fault code and capture the input signal supplied by theengine coolant temperature sensor, the engine load calculation and the engine speed at thetime of failure. TestBook/T4 will display the live readings from the CMP sensor.Ambient Barometric Pressure SensorThe ECM incorporates an integral ambient barometric pressure sensor. This internal sensor issupplied with a 5V feed and returns a linear voltage of between 2.4 and 4.5 Volts. Thisrepresents the barometric pressure.The system monitors barometric pressure for the following reasons: The barometric pressure along with the calculated air mass provides additional correctionfor refining injection “ON” time The value provides a base value for the ECM to calculate the air mass being injected intothe exhaust system by the secondary air injection system. This correction factor changesthe secondary air injection “ON” time which in turn optimizes the necessary air flow into theexhaust system The signal is used to recognize down hill driving and to postpone the start of evaporativeemission leakage diagnosis.Engine Coolant Temperature (ECT) SensorThe ECT sensor is located front of the engine, adjacent to the thermostat housing. The sensorincorporates two Negative Temperature Coefficient (NTC) thermistors and four electricalconnections. One set of connections are used by the ECM while the other set are used by theinstrument pack temperature gauge.ECT SensorEach thermistor used forms part of a voltage divider circuit operating with a regulated 5 V feedand an earth.184

BOSCH ME 7.2 ENGINE MANAGEMENTThe signal supplied by the ECT sensor is critical to many fuel and ignition control strategies.Therefore, the ECM incorporates a complex ECT sensor default strategy, which it implements inthe event of failure. The ECM uses a software model, based on the time the engine has beenrunning and the air intake temperature, to provide a changing default value during the enginewarm-up. When the software model calculates the coolant temperature has reached 60 C (140 F), a fixed default value of 85 C (185 F

BOSCH ME 7.2 ENGINE MANAGEMENT Bosch ME 7.2 ENGINE MANAGEMENT 171 BOSCH ME 7.2 ENGINE MANAGEMENT Introduction The Bosch ME 7.2 engine management

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