ISAT Scan Tool Communication

Fault Symptom
Communication between the ISAT scan tool and the transmission control module cannot be established.





Procedure
1. Check the ISAT scan tool's connection
Plug the ISAT scan tool into the car's data link connector.

Does the ISAT scan tool display light up?

YES: Proceed to point 4.
NO: Check that fuse 13 is intact and continue with point 2.

2. Check the current (+30 circuit) supplied to the data link connector.

Connect a test lamp to pin 16 of the data link connector and a good grounding point. The test lamp should light up if current (+30 circuit) is present.

Is the lamp on?

YES: Continue with point 3.
NO: Check and, if necessary, rectify the wiring between pin 16 and fuse 13. If the wiring is OK, continue fault diagnosis as described in the +30 power supply, electrical system wiring diagrams.





3. Check the ground connection in the data link connector.

- Connect a test lamp to pins 5 and 16 of the data link connector.
- Connect a test lamp to pins 4 and 16 of the data link connector.
In both cases the test lamp should light up if there is a connection to ground.

Is the lamp on?

YES: Check the ISAT scan tool.
NO: Repair or replace the wiring between pin 5 and grounding point G33S or else between pin 4 and grounding point G33P.

4. Check the ISAT scan tool's connection to the transmission

Select "AUT TRANSMISSION". The ISAT scan tool should then display the menu for the transmission.

Is the menu displayed?

YES: Proceed to point 7.
NO: Continue with point 5.

5. Check the ISAT scan tool's connection to another system

Choose any of the car's other systems, such as Integrated Central Electronics (ICE). The ISAT scan tool should display the menu for the chosen system.

Is the menu displayed?

YES: Continue with point 6.
NO: Check the ISAT scan tool.





6. Check The Wiring harness
Check the continuity of the wiring harness between pin 7 of the data link connector and pin 23 of the transmission control module. The resistance should be < 1 ohm.

Is the resistance OK?

YES: Continue with point 7.
NO: Repair or replace the wiring harness and continue with point 7.

7. Final check
Select "AUT TRANSMISSION". The ISAT scan tool should now display the menu for the automatic transmission.

Is the menu displayed?

YES: The remedial action taken was correct.
NO: Continue as described under "Before Changing A Control Module". Before Changing A Control Module