Scan Tool Unable To Contact Control Module

DIAGNOSTIC COMMUNICATION
ISAT SCAN TOOL INPUT AND OUTPUT SIGNALS





Basic Requirement.
ISAT scan tool communication with the Motronic works satisfactorily in another car.

Fault Symptom.
No contact with the Motronic control module via the ISAT scan tool.





Diagnostic Procedure.
1. Check the data link connector's ground connection and power supply
- Connect a test lamp to:
^ pin 16 and a good grounding point: B+
^ pin 16 and pin 4: B+
^ pin 16 and pin 5: B+

Did the test lamp light up in all three tests?
YES: Continue with point 2.
NO: Repair or replace the lead in question and proceed to point 3.





2. Check the communications lead
- Turn the ignition switch to the OFF position.
- Connect a test lamp to pins 16 and 7. The test lamp should not light up.
- Unplug the Motronic control module's connector and ground pin 88.

The test lamp should light up.

Test lamp on as above?
YES: Continue with point 3.
NO: Repair or replace the wiring connected to data link connector pin 7.





3. Final check
- Ignition switch in the ON position.
- Connect the ISAT Scan Tool.
- Contact the Motronic system.

The ISAT scan tool should show the Motronic menu.

Is contact established?
YES: The steps taken to rectify the fault were correct.
NO: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics