Instrument Cluster / Carrier

B1730

Fuel consumption

Fault symptoms
Calculated fuel consumption in SID incorrect.

Condition
Break/short circuit in signal lead from the engine management system at engine speeds above 300 rpm for longer than 25 seconds.

Diagnostic help
A reading of "Fuel consumed" can be obtained with the diagnostic tool.

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. Check the fault symptoms






Is the "CHECK ENGINE" lamp on in the main instrument unit?
YES
- See fault diagnosis in Computers and Control Systems.
NO
- Go to step 2.

2. Check the control module signal input
- Unplug connector: Main instrument unit (22-pin connector): (540).






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






- Run the starter motor for 10 seconds.






- The test lamp should flash.






Is the function correct?
YES
- Go to step 7.
NO
- Go to step 3.

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






TRIONIC
- Go to step 4
MOTRONIC 2.10.3
- Go to step 5

4. Check the wiring, Trionic
- Check the lead between pin 11 of the MIU's 22- pin connector and pin 5 of the Trionic.






Is the lead OK?
YES
- Go to step 6.
NO
- Repair or replace the lead between pin 11 of the MIU's 22-pin connector and pin 5 of the Trionic.
- Go to step 7.

5. Check the wiring, Motronic
- Check the lead between pin 11 of the MIU's 22-pin connector and pin 16 of the Motronic.






Is the lead OK?
YES
- Go to step 8.
NO
- Repair or replace the lead between pin 11 of the MIU's 22-pin connector and pin 16 of the Motronic.
- Go to step 7.

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






- Carry out a drive cycle:
- Drive the car at varying engine loads and rpm for five minutes.






- Evaluate the drive cycle:
- Check that no diagnostic trouble codes recur.






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

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






- Perform a functional test.






- Check that no diagnostic trouble codes recur.






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

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






- Carry out a drive cycle:
- Drive the car at varying engine loads and rpm for five minutes.






- Evaluate the drive cycle:
- Check that no diagnostic trouble codes recur.






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