Tachometer Out Of Order

OUTPUT SIGNAL TO MAIN INSTRUMENT DISPLAY PANEL





Fault Symptom.
Tachometer out of order.
If a TCS/TCM diagnostic trouble code is present, follow the diagnostic procedure described for that trouble code.

Diagnostic Help.
The tachometer can be activated with the ISAT scan tool.

- Select "ACTIVATE.
- Select "ENGINE RPM".
The command activates the Motronic control module, causing it to send a 50 Hz signal to the tachometer. The tachometer should then indicate about 1000 rpm for 30 seconds.





Diagnostic Procedure.
1 Check the control module connection

- Unplug the main instrument display panel connector.
- Take a voltage/frequency reading across:
^ pin 6 and battery negative (B-).
- Connect an ISAT scan tool.
- Turn the ignition switch to the ON position.
- Select "ACTIVATE".
- Select "ENGINE RPM".
The command activates output voltage, which should be about 5.5 - 6 V and 50 Hz.

Is the reading OK?

YES
^ Continue fault diagnosis in the electrical system main instrument display panel.
NO
^ Continue with point 2.

2 Check The Wiring

- Check the continuity of the wiring between pin 47 of the Motronic control module and pin 6 of the main instrument display panel.

Is the wiring OK?

YES
^ Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO
^ Repair or replace the wiring.