Check Engine Warning Lamp

CHECK ENGINE Warning Lamp

Fault symptoms
The CHECK ENGINE indicator lamp is inoperative.

Diagnostic help
The indicator lamp can be activated with the diagnostic tool.
Contact the engine management system concerned.
- Select "Activate"
- Select "CHECK ENGINE lamp"

Check the wiring harness
Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short-circuits in the leads. Observe the multimeter, test lamp or diagnostic tool during the test.

Diagnostic procedure

1. Choose the system
- Select the engine management system.






TRIONIC
- Go to step 2.

MOTRONIC 2.10.3
- Go to step 4.

2. Check the control module input, Trionic
- Unplug connector: Main instrument unit's 20-pin connector: (540).






- Connect test lamp 86 11 857 to B+ and pin 8 of the female connector.






- Turn the ignition switch to ON.






- Contact Trionic.






- Activate: CHECK ENGINE Lamp (ON).
- The test lamp should light up.






Is the function correct?
YES
- Check and replace faulty bulb.
- Go to step 5.
NO
- Repair or replace the lead between pin 8 of the MIU's 20-pin connector and Trionic pin 32.
- Go to step 3.

3. Final check
- Clear the diagnostic trouble codes in all systems.






- Perform a functional test.






Is the function correct?
YES
- The steps taken to rectify the fault were correct.
NO
- See "Before changing a control module."

4. Check the control module input, Motronic
- Unplug connector: Main instrument unit's 20-pin connector: (540).






- Connect test lamp 86 11 857 to B+ and pin 8 of the female connector.






- Turn the ignition switch to ON.






- Contact Motronic.





- Activate: CHECK ENGINE Lamp (ON).
- The test lamp should light up.






Is the function correct?
YES
- Check and change the faulty bulb.
- Go to step 5.
NO
- Repair or replace the lead between pin 8 of the MIU's 20 - pin connector and pin 21 of the Motronic.
- Go to step 6.

5. Final check
- Clear the diagnostic trouble codes in all systems.






- Perform a functional test.






Is the function correct?
YES
- The steps taken to rectify the fault were correct.
NO
- See Fault diagnosis, general, "Before changing a control module."

6. Final check
- Clear the diagnostic trouble codes in all systems.






- Perform a functional test.






Is the function correct?
YES
- The steps taken to rectify the fault were correct.
NO
- See "Before changing a control module." Before Changing A Control Module