Engine management system - V8 (Immobilisation system): Description and operation
- Make
- Land Rover
- Model
- Discovery II (UK)
- Section
- Description and operation › Immobilisation system
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: l 'New'. l 'Secure'. l '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 |
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