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No communication with TCM (cars with Trionic T5 or Motronic engine management system)

Read the instructions below then start the fault diagnostic procedure.

Symptom: No communication with TCM

No communication with TCM (cars with Trionic T5 or Motronic engine management system)



Fault symptoms

No communication with TCM

Conditions

The following conditions are applicable:


• Ignition switch in ON position


Diagnostic help

First, check the fuses for the TCM control module and that the data link connector pins for communication are in place.

Then, check whether the TCM is awake and allowing diagnostics communication. If not, check to see if the diagnostic tool works in another car.

If no fault is found, rectify the communications lead between TCM and the data link connector.

Check wiring harness.

Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short-circuits in the leads. Observe the multimeter, test lamp or diagnostic tool during the test.