44660/24660
Diagnostic trouble codes 44660/24660PRE-IGNition
Fault symptom
- High fuel consumption.
- Jerkiness in connection with fuel enrichment may occur.
Conditions
The DI/APC control module has recorded PRE- IGNition.
Diagnostic procedure
1 Check the spark plugs
- Check that the spark plugs are of the right type and have the correct heat range. Specifications
Are the spark plugs OK?
YES Continue with point 2.
NO Change the spark plugs and continue with point 3.
2 Check other possible causes
Check the following possible causes:
- fuel pressure
- pump flow capacity
- injector flow rate
Check the valves for possible damage by carrying out a compression test.
Any of the above faults present?
YES Rectify the fault and continue with point 3.
NO Change the spark plugs and continue with point 3.
3 Final check
- Clear the diagnostic trouble code.
- Implementation of driving cycle:
Drive the car at varying engine loads and rpm for 5 minutes.
- Evaluation of driving cycle:
Check whether the diagnostic trouble code recurs.
Does the diagnostic trouble code recur?
YES Continue with "Before Control Module Replacement". Service and Repair
NO The steps taken to rectify the fault were correct.
Engine power down or high fuel consumption
The performance of M89-M90 cars may suffer as a result of the DI/APC control module erroneously detecting PRE-IGNition signals. The signals are passed on to the LH control module with a request for fuel enrichment which leads to an excessively rich fuel-air mixture with loss of power and lump idling as a result.
If the above symptoms occur the following steps can be taken:
Important: On M91 and later cars the problem has been eliminated and the lead also serves other purposes. The lead cannot therefore be disconnected.
1 Check the DI/APC control module's status code to ascertain the correct cause of the fault.
2 Connect the ISAT scan tool to the black data link connector and carry out diagnosis on system 2. In the event of diagnostic trouble code 44660/24660 for PRE-IGNition, clear the control module's memory with the engine running. Then continue as described below.
3 Break the connection between DI/APC control module pin 26 and LH control module pin 20 (LH 2.2) or pin 28 (LH 2.4), as follows:
Withdraw and insulate the socket contact for the VT lead (terminal 8) from the rear of the 10-pin connector under the left-hand front seat.
4 Drive the car on test and check that its performance has been restored.
Important: If the control module's connector has been unplugged, make sure it is refitted the right way round. It is possible to plug it in the wrong way round, which would damage the control module.