Discovery 2. Manual — part 466
ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION
18-1-7
Engine Control Module (ECM)
The ECM is made from aluminium alloy and is located in the engine compartment on the RH side inner wing. The
ECM has an interface of 72 pins via two connectors providing both input information and output control. The ECM
receives information from the sensors to inform it of the current state of the engine. The ECM then refers this
information to stored values in its memory and makes any changes to the operation of the engine as necessary via
the actuators. This is a rolling process and is called adaptive strategy. By using this adaptive strategy the ECM is
able to control the engine to give optimum driveability throughout all operating conditions. There is no ECM self test,
although the ECM saves driveability data from the last journey. Power down of the ECM can take between 10 seconds
and 10 minutes dependent on coolant temperature.
ENGINE MANAGEMENT SYSTEM - TD5
18-1-8
DESCRIPTION AND OPERATION
Input/Output
ECM inputs and outputs are detailed below:
Connector C0158
Pin No.
Input/Output
Function
Signal type
Value
Interfaces
A1
Output
Injector 5
Analogue
0
A2
Not used
A3
Output
EGR modulator
Digital
0-12
A4
Not used
A5
Input
FT sensor earth
0 volts
0
A6
Input
MAP sensor
Analogue
0-5 volts
A7
Input
ECT sensor
Analogue
0-5 volts
A8
Sensor supply
Sensor supply
5 volts
5 volts
A9
HT pin
A10
Input
AAP sensor
Analogue
0-5 volts
A11
Input
MAF sensor
Analogue
0-5 volts
A12
Not used
A13
Input
CKP sensor positive
Analogue
A14
Not used
A15
Input
Sensor earth 5
0 volts
0 volts
A16
Input
CKP sensor screened earth
0 volts
0 volts
A17
Input
Sensor earth 6
0 volts
0 volts
A18
Input
Sensor earth 3
0 volts
0 volts
A19
Input
FT sensor
Analogue
0-5 volts
A20
Input
Sensor earth 2
0 volts
0 volts
A21
Output
Turbocharger wastegate
modulator
Digital
0-12 volts
A22
Output
Injector common 2
Analogue
0-85 volts
A23
Output
Injector common 1
Analogue
0-85 volts
A24
Output
Injector 4
Analogue
0 volts
A25
Output
Injector 1
Analogue
0 volts
A26
Output
Injector 2
Analogue
0 volts
A27
Output
Injector 3
Analogue
0 volts
A28
Not used
A29
Output
Glow plug relay
Analogue
0-90 volts
A30
Input
Sensor earth 4
0 volts
0 volts
A31
Not used
A32
Input/Output
CAN negative
Digital
2.5-5 volts
EAT
A33
Input
High/low ratio switch
Digital
0-5 volts
EAT, SLABS
A34
Input
IAT sensor
Analogue
0-5 volts
A35
Input/Output
Can positive
Digital
2.5-5 volts
EAT
A36
Input
CKP sensor negative
0 volts
0 volts
ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION
18-1-9
Connector C0658
Pin No.
Input/Output
Function
Signal type
Value
Interfaces
B1
Input
Earth 1
0 volts
0 volts
B2
Input
Earth 4
0 volts
0 volts
B3
Input
Supply battery voltage
12 volts
12 volts
B4
Output
Cooling fan relay
Switch
12-0 volts
A/C ECU
B5
Output
Fuel pump relay
Switch
12-0 volts
B6
Output
MIL
Switch
12-0 volts
Instruments
B7
Output
Temperature gauge
Digital
0-12 volts
Instruments
B8
Not used
B9
Input
A/C clutch request
Switch
12-0 volts
A/C ECU
B10
Input
Normally closed brake
switch
Switch
12-0 volts
B11
Input
Cruise control SET+ switch
Switch
12-0 volts
B12
Input
TP sensor 1
Analogue
0- 5 volts
B13
Input
Vehicle speed
Digital
0-12 volts
B14
Input
TP sensor supply
5 volts
5 volts
B15
Input
Cruise control master switch
Switch
12-0 volts
B16
Input
Normally open brake switch
Switch
0-12 volts
B17
Input
Cruise control RES switch
Switch
12-0 volts
B18
Input/Output
Serial communication link
Digital
0-12 volts
All ECU's
B19
Output
Tachometer engine speed
Digital
0-12 volts
Instrument
Cluster
B20
Not used
B21
Output
Main relay
Switch
0-12 volts
B22
Input
Supply battery voltage
12 volts
12 volts
B23
Input
A/C fan request
Switch
12-0 volts
B24
Input
Earth 3
0 volts
0 volt
B25
Input
Earth 2
0 volts
0 volts
B26
Input
TP sensor earth
0 volts
0 volts
B27
Input
Supply 2
12 volts
12 volts
B28
Not used
B29
Output
A/C relay
Switch
12-0 volts
B30
Output
Glow plug warning light
Switch
12-0 volts
Instrument
Cluster
B31
Not used
B32
Output
ABS
digital
0-5 volts
SLABS
B33
Input
Ignition
Switch
0-12 volts
B34
Input
Security code
digital
0-5 volts
B35
Input
Clutch switch
Switch
12-0 volts
B36
Input
TP sensor 2
Analogue
5-0 volts
ENGINE MANAGEMENT SYSTEM - TD5
18-1-10 DESCRIPTION AND OPERATION
Mass Air Flow (MAF) sensor
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM uses
the information generated by the MAF to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film. One
element is controlled at ambient temperature e.g. 25
°
C (77
°
F) while the other is heated to 200
°
C (392
°
F) above
this temperature e.g. 225
°
C (437
°
F). As air passes through the MAF sensor the hot film will be cooled. The current
required to keep the constant 200
°
C (392
°
F) difference provides a precise although non-linear signal of the air drawn
into the engine. The MAF sensor sends a voltage between 0 and 5 volts to the ECM proportional to the mass of the
incoming air. This calculation allows the ECM to set the EGR ratio for varying operating conditions.
Input/Output
The MAF sensor receives battery voltage from the main relay in the engine compartment fuse box. Signal output from
the MAF sensor to the ECM is a variable voltage proportional to air drawn into the engine.
Input to the MAF sensor is via pin 5 of connector C0570 at the engine compartment fuse box. This 12 volt supply is
provided by the main relay via fuse 2 in the engine compartment fuse box. The MAF sensor receives the input voltage
at pin 3 of the sensor connector.
Output from the MAF sensor is measured at pin 11 of the ECM connector C0158. The earth path is via pin 20 of the
ECM connector C0158.
The MAF sensor can fail the following ways or supply incorrect signal:
l
Sensor open circuit.
l
Short circuit to vehicle supply.
l
Short circuit to vehicle earth.
l
Contaminated sensor element.
l
Damaged sensor element.
l
Damaged in wiring harness.
l
MAF supplies incorrect signal (due to air leak or air inlet restriction).
In the event of a MAF sensor signal failure any of the following symptoms may be observed:
l
During driving engine speed may dip, before recovering.
l
Difficult starting.
l
Engine stalls after starting.
l
Delayed throttle response.
l
EGR inoperative.
l
Reduced engine performance.
l
MAF signal out of parameters.
The MIL will not illuminate in a MAF sensor failure, and the ECM will use a fixed default value from its memory.
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