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Diagnostics instrument communication, checking

Symptom: Communication between the Scan tool diagnostics instrument and the control module cannot be established.

Diagnostics instrument communication, checking

Fault symptom

Communication between the Scan tool diagnostics instrument and the control module cannot be established.



Diagnostic procedure

1 Checking the diagnostics instrument's connection



Connect the Scan tool diagnostics instrument to the car's data link connector.

Is the diagnostics instrument display alight?

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.

Did the lamp light up?

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" section of Service Manual 3:2 "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.


Did the lamp light up?

yes

Check the diagnostics instrument.


no

Repair or replace the wiring between pin 5 and grounding point G33S or else between pin 4 and grounding point G33P (LHD) or G34P (RHD).


4 Checking the diagnostics instrument's communication with the transmission


Select "AUT TRANSMISSION". The diagnostics instrument should now show the menu for the transmission, see .

Is the menu displayed?

yes

Continue with step 7.


no

Continue with point 5.


5 Checking the diagnostics instrument's communication with another system


Select one of the car's other systems, such as ICE. The diagnostics instrument should show the menu for the selected system.

Is the menu displayed?

yes

Continue with step 6.


no

Check the diagnostics instrument.


6 Checking 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 correct?

yes

Continue with step 7.


no

Repair or replace the wiring harness and continue with point 7.


7 Final check


Select "AUT TRANSMISSION". The diagnostics instrument should now show the automatic transmission menu.

Is the menu displayed?

yes

The remedial action taken was correct.


no

Continue with .