Discovery 2. Manual - part 493

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-51

Should a malfunction of the rough road signal occur, the following fault codes may be evident and can be retrieved
by TestBook:

Hill Descent Control (HDC) signal
The ECM transmits throttle angle, engine torque, engine identification (Td5 or V8), and transmission type (automatic
or manual) data to the SLABS ECU to support the Hill Descent Control system. The information is transmitted via a
0 – 12V pulse width modulated (PWM) signal at a frequency of 179.27 Hz.

Function
The HDC signal output from the ECM is via pin 29 of connector C0636. The ECM generates a PWM signal that varies
in pulse width in accordance with changing throttle angle or engine torque. The throttle angle data is transmitted on
pulses 1, 3, 5 and 37. The engine torque data is transmitted on pulses 2,4,6 and 38. The engine and transmission
information is transmitted on pulse 39. A synchronising pulse is transmitted after every 39th pulse.

The HDC signal can fail in the following ways:

Harness or connector damage

A HDC signal failure may be evident from the following:

HDC / ABS warning light on

HDC inoperative

Audible warning

Should a malfunction of the HDC signal occur, the following fault codes may be evident and can be retrieved by
TestBook:

Low fuel level signal
When the fuel level in the fuel tank becomes low enough to illuminate the low fuel level warning lamp in the instrument
cluster, the instrument cluster generates a low fuel level signal. If the low fuel level signal is present during the ECM
misfire detection function the ECM can use it to check for a 'false misfire'.

Conditions
The fuel sender generates the low fuel level signal when the fuel sender resistance is greater than 158

8 ohms.

P Code

J2012 Description

Land Rover Description

P1590

ABS rough road signal circuit malfunction

Hardware is OK, but SLABS ECU is sending an error
signal

P1591

ABS rough road signal circuit low

Signal from SLABS ECU short circuit to earth

P1592

ABS rough road signal circuit high

Signal from SLABS ECU short circuit to vehicle battery
supply

P Code

J2012 Description

Land Rover Description

P1663

Throttle angle/Torque signal circuit malfunction

SLABS HDC link open circuit

P1664

Throttle angle/Torque signal circuit low

SLABS HDC link short circuit to ground

P1665

Throttle angle/Torque signal circuit high

SLABS HDC link short circuit to battery voltage

ENGINE MANAGEMENT SYSTEM - V8

18-2-52 DESCRIPTION AND OPERATION

Function
The illumination of the low fuel level warning lamp in the instrument cluster triggers the low fuel level signal to be sent
to the ECM. This signal is processed via pin 8 of connector C0637 of the ECM.

Should a misfire occur while the fuel level is low, the following fault code may be evident and can be retrieved by
TestBook.

Coolant temperature gauge signal
The ECM controls the temperature gauge in the instrument cluster. The ECM sends a coolant temperature signal to
the temperature gauge in the instrument cluster in the form of a PWM square wave signal.

The frequency of the signal determines the level of the temperature gauge.

Conditions
The ECM operates the PWM signal under the following parameters:

-40

C (-40

F) = a pulse width of 768

140

C (284

F) = a pulse width of 4848

Function
The coolant temperature signal is an output from the ECM to the instrument cluster. The coolant temperature signal
is generated via pin 44 of connector C0636 of the ECM.

The coolant temperature signal can fail in the following ways:

Wiring short circuit to vehicle supply.

Wiring short circuit to vehicle earth.

Wiring open circuit.

In the event of a coolant temperature signal failure any of the following symptoms may be observed:

Coolant temperature gauge will read cold at all times.

Coolant temperature warning lamp remains on at all times.

Controller Area Network (CAN) system
The controller area network (CAN) system is a high speed serial interface between the ECM and the Electronic
Automatic Transmission (EAT) ECU. The CAN system uses a 'data bus' to transmit information messages between
the ECM and the EAT ECU. Because there are only two components in this CAN system, one will transmit information
messages and the other will receive information messages, and vice-versa.

Conditions
The CAN system is used by the EAT ECU and the ECM for transmission of the following information:

Gearshift torque control information.

EAT OBD information.

MIL request.

Vehicle speed signal.

Engine temperature.

Engine torque and speed.

Gear selected.

Gear change information.

Altitude adaptation factor

Air intake temperature

Throttle angle / pedal position

P Code

J2012 Description

Land Rover Description

P1319

Misfire detected at low fuel level

Misfire detected with low fuel level

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-53

Function
The CAN system uses a twisted pair of wires to form the 'data bus' to minimise electrical interference. This method of
serial interface is very reliable and very fast. The information messages are structured so that each of the receivers
(ECM or EAT ECU) is able to interpret and react to the messages sent.

The CAN 'data bus' is directly connected between pin 36 of connector C0637 of the ECM and pin 16 of connector
C0193 at the EAT ECU, and pin 37 of connector C0637 of the ECM and pin 44 of connector C0193 at the EAT ECU.

The CAN system can fail in the following ways:

CAN data bus wiring open circuit.

CAN data bus wiring short circuit.

In the event of a CAN data bus failure any of the following symptoms may be observed:

MIL illuminated after 2 drive cycles (NAS only).

EAT defaults to 3rd gear only.

Harsh gearshifts.

'Sport' and 'manual' lights flash alternately.

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by
TestBook.

Drive cycles
The following are the TestBook drive cycles:

Drive cycle A:

1 Switch on the ignition for 30 seconds.
2 Ensure engine coolant temperature is less than 60

C (140

F).

3 Start the engine and allow to idle for 2 minutes.
4 Connect TestBook and check for fault codes.

Drive cycle B:

1 Switch ignition on for 30 seconds.
2 Ensure engine coolant temperature is less than 60

C (140

F).

3 Start the engine and allow to idle for 2 minutes.
4 Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5 Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6 Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7 Allow engine to idle for 2 minutes.
8 Connect TestBook and with the engine still running, check for fault codes.

P Code

J2012 Description

Land Rover Description

P0600

Serial communication link malfunction

CAN time out

P1776

Transmission control system torque interface
malfunction

EAT torque interface error

ENGINE MANAGEMENT SYSTEM - V8

18-2-54 DESCRIPTION AND OPERATION

Drive cycle C:

1 Switch ignition on for 30 seconds.
2 Ensure engine coolant temperature is less than 60

C (140

F).

3 Start the engine and allow to idle for 2 minutes.
4 Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5 Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6 Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7 Cruise at 60 mph (100 km/h) for 8 minutes.
8 Cruise at 50 mph (80 km/h) for 3 minutes.
9 Allow engine to idle for 3 minutes.

10 Connect TestBook and with the engine still running, check for fault codes.

NOTE: The following areas have an associated readiness test which must be flagged as complete, before a problem
resolution can be verified:

catalytic converter fault;

Evaporative loss system fault;

sensor fault;

sensor heater fault.

When carrying out a drive cycle C to determine a fault in any of the above areas, select the readiness test icon to
verify that the test has been flagged as complete.

Drive cycle D:

1 Switch ignition on for 30 seconds.
2 Ensure engine coolant temperature is less than 35

C (95

F).

3 Start the engine and allow to idle for 2 minutes.
4 Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5 Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6 Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7 Cruise at 60 mph (100 km/h) for 5 minutes.
8 Cruise at 50 mph (80 km/h) for 5 minutes.
9 Cruise at 35 mph (60 km/h) for 5 minutes.

10 Allow engine to idle for 2 minutes.
11 Connect TestBook and check for fault codes.

Drive cycle E:

1 Ensure fuel tank is at least a quarter full.
2 Carry out Drive Cycle A.
3 Switch off ignition.
4 Leave vehicle undisturbed for 20 minutes.
5 Switch on ignition.
6 Connect TestBook and check for fault codes.

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