Fault Symptoms

No Bus Communication With The TCM:

Fault symptoms
No bus communication with the TCM.

Conditions
The following conditions are applicable:

Trionic:
- Engine Running
- The TCM has previously been present on the bus at one time.
- No communication for 3 seconds.

Diagnostic help
Some of the following symptoms may be observable:

- Diagnostic trouble code P1921 in TCM (if TCM can be contacted).
- Additional diagnostic trouble codes in Trionic (P1908).
- Engine will not start.
- Automatic transmission in limp-home mode (CHECK GEAR BOX lamp on)







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.