Fault Conditions

No Bus Data From TCM. See Fault Tracing, Bus and Diagnostic Communication.
See Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Procedures/Fault Diagnosis, Diagnostic Trouble Codes/P1923 No Bus Communication with the TCM.







Fault symptoms
Some of the following symptoms may be observed:
- Engine will not start.
- CHECK ENGINE.
- Automatic transmission not shifting gear.
- CHECK GEAR BOX.
- Additional trouble codes in Trionic (P1624 or P1908).
- DTC P1921 or P1902 in TCM (if TCM can be contacted).

On-Board Diagnostics
Type of diagnosis:
- Continuous. But interrupted when fault criteria fulfilled and will not restart until next driving cycle.

Enable criteria:
- Engine running. TCM has previously been on the bus on some occasion.

Fault criteria:
- No communication for more than 3 s.

Dependents:
- None.

System reaction to a fault:
- Max. engine torque (Bus from TCM) set to 310 Nm.

OK report:
- Enable criteria fulfilled and fault criteria not fulfilled within 60 s.

Fault handling: Fault Handling III, Other Emission-Related Component & Function
- Type III.

Diagnostic help
Fault diagnosis concerns an intermittent electrical fault in the power supply to the transmitting control module or any of the bus leads.

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

Diagnostic procedure
For more detailed fault diagnosis, see "Bus and diagnostic communication P1923".
See Powertrain Management/Computers and Control Systems/Information Bus/Testing and Inspection/Procedures/Fault Diagnosis, Diagnostic Trouble Codes/P1923 No Bus Communication with the TCM.