OPERATING PRINCIPLE -
BOSCH ME7.4.4 / M7.4.4
AND EOBD
DOCUMENT REF N°: 1.3.277 September 2000
DEALER QUALITY
1
NOTE TO READERS
This document contains information of a confidential nature. It is therefore strictly reserved for the use of CITROËN trainers and may not be distributed to people outside the relevant departments.
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BROCHURE SUMMARY
OPERATING PRINCIPLE - BOSCH ME7.4.4/M7.4.4 AND EOBD
The aim of this document is to define the composition and operation of the BOSCH ME7.4.4 and M.7.4.4 petrol engine management systems.
These devices consist of a digital ECU which analyses information from the various sensors and then operates the injectors and ignition coils at the right moment. It is also responsible for operating the petrol vapour recycling electrovalve, the gas throttle or idle regulation motor and an air injection to the exhaust pump.
The following subjects will be dealt with in this document:
- General details and presentation of the systems.
- Description and operation of the components.
- Wiring diagrams.
- Diagnostics.
EOBD is dealt with at the end of the document.
CONTENTS
Chapter 1: foreword 1
Chapter 2: DESCRIPTION of the components 9
I - INLET AIR PRESSURE SENSOR 9
II - Engine speed sensor 11
III - knock sensor 13
IV - Motorised throttle housing (ME7.4.4) 14
V - Accelerator pedal position sensor (ME7.4.4) 18
VI - Coolant temperature sensor 20
VII - coolant temperature Thermocontact 22
VIII - Pressurestat 23
IX - ignition coil 24
X - power steering oil pressure switch * 26
XI - fuel pressure regulator 27
XII - injectors 28
XIII - fuel pump 28
XIV - fuel filter 29
XIV - double multifunction relay 30
XVI - canister reservoir 31
XIX - downstream oxygen sensor 34
XX - catalytic converter 36
XXI - stepper motor ( M7.4.4 ) 37
Chapter 3: diagnostic assistance 43
I - Identification 43
II - history 44
III - read faults 44
IV - associated variables 47
V - erase faults 47
VI - PARAMETER MEASUREMENT 48
VII - actuator tests 50
VIII - Initialising autoadaptives 51
IX - telecoding 52
X - downloading 53
Chapter 4: wiring diagram 55
I - layout diagram 55
II - parts list 56
Chapter 5: eobd - GENERAL details 57
Chapter 6: operating faults detected 59
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Chapter 1
foreword
The ME7.4.4 and M7.4.4 ignition-injection ECUs have been developed to control the following functions:
· engine torque,
· sequential multipoint injection,
· twin static ignition,
· cruise control (optional),
· L4 (EOBD)*/K'/ifL5 depollution standards,
· engine cooling,
· dialogue with the other ECUs on the CAN multiplexed network (automatic gearbox, ESP, BSI etc for ME7.4.4)(automatic gearbox only for M7.4.4 ).
They both have 3 modular connectors with a total of 112 channels.
They are fitted to the following engines:
· Bosch ME7.4.4: TU5JP4,
· Bosch M7.4.4: TU1JP and TU5JP.
They belong to the new ECUs which can communicate with the vehicle's other ECUs (automatic gearbox, BSI, ESP, etc) using a standard protocol called the CAN (Controller Area Network).
The dialogue with these various ECUs depends on the vehicle type and its equipment level.
The Bosch ME7.4.4 and M7.4.4 ECUs comply with the new standard which came into force on 1st January 2000 regarding the on-board diagnosis of pollutant emissions.
This standard is called EOBD (European On Board Diagnosis).
K' depollution:
· the downstream oxygen sensor is discontinued,
· the upstream oxygen sensor is lead resistant,
· the catalytic converter is not impregnated,
· the EOBD standard does not apply to this depollution level.
ifL5 depollution:
The engine is fitted with an air pump to comply with the L5 depollution standard.
(L5 applicable from 1st January 2005).
By using the information from the various sensors, they perform the following functions:
Calculation of the injection time, phasing and control of the injectors as a function of the following parameters:
· driver's wishes (pedal position sensor for ME7.4.4 and throttle potentiometer for M7.4.4, cruise control, electronic stability program),
· thermal state of the engine (coolant temperature sensor),
· mass of air absorbed (inlet air temperature sensor, inlet air pressure sensor and engine speed sensor),
· engine operating conditions: starting, idling, stabilised engine speed, transitory engine speeds, injection cut-off and power take-up speed (motorised throttle for ME7.4.4 and stepper motor for M7.4.4, engine speed sensor, speed information),
· richness regulation (oxygen sensors)(2 sensors for L4 and ifL5 depollution and 1 sensor for K' depollution),
· canister circuit bleed (canister bleed electrovalve),
· inlet pressure (inlet air pressure sensor),
· battery voltage (battery),
· knock detection (knock sensor),
· cylinder n°1 position (phase detection integrated into the ignition).
Calculation of the advance and control of the ignition as a function of the following parameters:
· engine speed and position (engine speed sensor),
· inlet pressure (inlet manifold pressure sensor),
· air conditioning compressor status (air conditioning ECU or built-in systems interface or pressurestat information),
· vehicle speed information (vehicle speed sensor or ABS ECU or ESP ECU),
· battery voltage.
Management of the following internal functions:
· idle regulation (stepper motor or motorised throttle),
· engine speed stability when idling and when not idling,
· fuel supply (fuel pump),
· supply to the sensors,
·...
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