Discovery 2. Manual - part 492

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-47

Function
All of the ECM's internal diagnostic fault paths are monitored by the OBD system. Specific faults have their own
numeric code relating to certain sensors or actuators etc. These specific faults fall into two types, error codes (E xxx)
or cycle codes (Z xxx). E codes represent instantaneous faults and Z codes relate to codes generated after completion
of a drive cycle.

If an emission relevant fault occurs on a drive cycle, the ECM stores a temporary fault code, if the fault does not occur
on subsequent drive cycles the fault code stays as a temporary fault code. If the fault recurs on subsequent drive
cycles the ECM stores the fault code as a permanent code, and depending on which component has failed the ECM
will illuminate the MIL.

Immobilisation system
The ECM and the body control unit (BCU) security system comprise the immobilisation system.

The ECM and the BCU combine to prevent the engine from running unless the appropriate security criteria are met.
The ECM and the BCU are a matched pair, if either one is replaced for any reason, the system will not operate unless
the replaced unit is correctly matched to its original specification. TestBook must be used to reconfigure the
immobilisation system.

Conditions
The ECM operates immobilisation in three states:

'New'.

'Secure'.

'No Code'.

Function
With the ECM operating in the 'New' state, TestBook is required to instruct the ECM to learn the new BCU code. If the
ECM is in delivery state (i.e. direct from the supplier), it will not run the vehicle and will store a new ECM fault code
when it is fitted. This code must be cleared after instructing the ECM to learn the BCU code using TestBook.

When the ECM is in the 'Secure' state, no further action is required as the ECM has successfully learned the BCU
code. A 'Secure' ECM can not be configured to a 'No Code' state.

If the vehicle is fitted with an ECM with a valid code, the engine will start and the MIL will go out.

However, if the ECM has an invalid BCU security code the engine will crank, start, and then immediately stall. The
status of the security system can only be interrogated using TestBook.

TestBook is able to retrieve the following immobilisation fault codes:

P Code

J2012 Description

Land Rover Description

P1666

Engine anti-theft signal circuit malfunction

BCU serial link frame/ bit timing error

P1667

Engine anti-theft signal circuit low

Serial link short circuit to earth

P1668

Engine anti-theft signal circuit high

Serial link open circuit

P1672

Engine anti-theft signal circuit wrong code
received

Secure ECM, received incorrect code

P1673

Engine anti-theft signal new engine control
module not configured

New ECM fitted

P1674

Engine anti-theft signal

No code ECM, valid code received

ENGINE MANAGEMENT SYSTEM - V8

18-2-48 DESCRIPTION AND OPERATION

Misfire detection
Due to increasing legislation, all new vehicles must be able to detect two specific levels of misfire.

Conditions
The ECM is able to carry out misfire detection as part of the OBD system using the following component parts:

Flywheel reluctor adaptation.

Calculation of engine roughness.

Detection of excess emissions misfire.

Detection of catalyst damaging misfire.

Function
The flywheel/ reluctor ring is divided into four segments 90

wide. The ECM misfire detection system uses information

generated by the CKP to determine crankshaft speed and position. If a misfire occurs, there will be an instantaneous
slight decrease in engine speed. The ECM misfire detection system is able to compare the length of time each 90

segment takes and is therefore able to pinpoint the source of the misfire.

For the ECM misfire detection system to be calibrated for the tolerances of the reluctor tooth positions, the flywheel/
reluctor ring must be 'adapted' as follows:

1800 - 3000 rev/min = speed range 1.

3000 - 3800 rev/min = speed range 2.

3800 - 4600 rev/min = speed range 3.

4600 - 5400 rev/min = speed range 4.

The ECM carries out flywheel/ reluctor ring adaptions across all the above speed ranges and can be monitored by
TestBook. The test should be carried out as follows:

Engine at normal operating temperature.

Select second gear (for both automatic and manual transmission vehicles).

Accelerate until engine rev limiter is operational.

Release throttle smoothly to allow engine to decelerate throughout the speed ranges.

Repeat process as necessary until all adaptations are complete.

TestBook is able to retrieve the following misfire detection fault codes:

P Code

J2012 Description

Land Rover Description

P0300

Random/multiple cylinder misfire detected

Excess emissions level of misfire on more than one
cylinder

P0301

Cylinder 1 misfire detected

Excess emissions level of misfire detected on cylinder
No.1

P0302

Cylinder 2 misfire detected

Excess emissions level of misfire detected on cylinder
No.2

P0303

Cylinder 3 misfire detected

Excess emissions level of misfire detected on cylinder
No.3

P0304

Cylinder 4 misfire detected

Excess emissions level of misfire detected on cylinder
No.4

P0305

Cylinder 5 misfire detected

Excess emissions level of misfire detected on cylinder
No.5

P0306

Cylinder 6 misfire detected

Excess emissions level of misfire detected on cylinder
No.6

P0307

Cylinder 7 misfire detected

Excess emissions level of misfire detected on cylinder
No.7

P0308

Cylinder 8 misfire detected

Excess emissions level of misfire detected on cylinder
No.8

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-49

TestBook is able to retrieve the following Catalyst damage fault codes:

The flywheel/ reluctor ring adaptions must be reset if the CKP sensor or the flywheel are changed.

Vehicle Speed Signal (VSS)
The VSS is used, by the ECM, to control idle speed and overrun cut off. The ECM receives the signal through a hard
wired connection direct from the SLABS ECU.

For vehicles fitted with an automatic gearbox, two vehicle speed signals are received by the ECM. The second signal
is derived from the main gearbox output shaft speed, and is sent to the ECM by the Electronic Automatic Transmission
(EAT) ECU though the Controller Area Network (CAN). The ECM compares the vehicle speed signal generated by
the SLABS ECU with that supplied via the CAN.

The ECM also receives transfer box information. This allows the ECM to take in to account the vehicle being driven
using low range gearing and compensate as necessary.

On vehicles with manual transmission, the SLABS signal is checked against a threshold value stored in ECM memory.
If other engine parameters indicate the engine is at high load and the VSS is below the threshold, a fault condition is
registered in the diagnostic memory.

The vehicle speed signal generated by the SLABS ECU is in the form of a pulse width modulated signal (PWM).
Pulses are generated at 8000 per mile, and the frequency of the signal changes in accordance with road speed. At
zero road speed the ECU outputs a reference signal at a frequency of 2Hz for diagnostic purposes.

Function
The input signal for the SLABS ECU is measured via pin 22 of connector C0637 of the ECM. The SLABS ECU
generates a PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile. For vehicles with
automatic gearbox the input signal for the EAT ECU is measured via pins 36 and 37 of connector C0637 of the ECM.
These pin numbers provide a bi-directional communications link using the CAN data bus.

P Code

J2012 Description

Land Rover Description

P1300

Misfire detected sufficient to cause catalyst
damage

Catalyst damaging level of misfire on more than one
cylinder

P1301

No description

Catalyst damaging level of misfire detected on cylinder
No.1

P1302

No description

Catalyst damaging level of misfire detected on cylinder
No.2

P1303

No description

Catalyst damaging level of misfire detected on cylinder
No.3

P1304

No description

Catalyst damaging level of misfire detected on cylinder
No.4

P1305

No description

Catalyst damaging level of misfire detected on cylinder
No.5

P1306

No description

Catalyst damaging level of misfire detected on cylinder
No.6

P1307

No description

Catalyst damaging level of misfire detected on cylinder
No.7

P1308

No description

Catalyst damaging level of misfire detected on cylinder
No.8

ENGINE MANAGEMENT SYSTEM - V8

18-2-50 DESCRIPTION AND OPERATION

In the case of a VSS failure on vehicles with automatic gearboxes, the ECM applies default values derived from the
EAT ECU. There are no default values for manual gearbox vehicles.

The VSS 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 VSS failure, any of the following symptoms may be observed:

MIL illuminated after 2 driving cycles (NAS only).

Vehicle speed limiting disabled (manual transmission vehicles only).

SLABS/HDC warning lamp on and audible warning.

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

Rough road signal
When the vehicle travels across rough terrain, or on rough roads instability becomes evident in the drive train. The
ECM could interpret these vibrations as a 'false misfire'. To counteract this 'false misfire' the SLABS ECU generates
a rough road signal, sends it to the ECM so that the ECM can suspend misfire detection for as long as the vehicle is
travelling on the 'rough road'.

Function
Input for the rough road signal is measured via pin 34 of connector C0637 of the ECM. The SLABS ECU generates
a PWM signal that varies in accordance with changing road conditions. The rough road PWM signal operates at a
frequency of 2.33 Hz

10%. The significance of changes in the PWM signal are shown in the following table:

The rough road signal can fail in the following ways:

Harness or connector damage

SLABS failure — wheel speed sensor

A rough road signal failure may be evident from the following:

HDC / ABS warning light on

P Code

J2012 Description

Land Rover Description

P0500

Vehicle speed sensor malfunction

VSS short or open circuit

P0501

Vehicle speed sensor range/performance

VSS implausible

PWM signal

Indication

<10%

Electrical short circuit to ground

25%

5 %

Smooth road

50%

5 %

SLABS error

75%

Rough road

>90%

Electrical short circuit to battery voltage

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