Tachometer Out Of Order

ENGINE SPEED
OUTPUT SIGNAL TO MAIN INSTRUMENT DISPLAY PANEL





Fault Symptoms.
Tachometer out of order. If a TCS/TCM diagnostic trouble code is present, proceed according to the diagnostic 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 the 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 5.5-6.0 V and 50 Hz.

Is the reading obtained 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 80 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.