Conditions

No Bus Data From TCM. See Fault Tracing 3:5 Bus and Diagnostic Communication.





Fault symptoms
Some of the following symptoms may perhaps be observed:
- Engine tails to start.
- CHECK ENGINE.
- Automatic transmission not shifting gear.
- CHECK GEAR BOX
- Additional trouble codes in Trionic (P1624 or P1908).
- Diagnostic trouble code P1921 or P1902 in TCM (if the 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 Comp. & Function
- Type III.

Diagnostic help
Fault diagnosis concerns intermittent electrical faults in the power supply for the sending control module or in a bus lead.

Check the wiring
Jiggle the leads and in-line connectors at various points and in different directions to detect any intermittent breaks or short circuit in the wiring. Observe the multimeter, test lamp or diagnostic tool while doing this.

Proceed to Diagnostic Procedures Reference