Conditions

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





Fault symptoms
Some of the following symptoms may perhaps be observed:
- Engine fails to start.
- Cruise Control does not work.
- A/C not working.
- Radiator fan runs continuously.
- Main instrument unit gauges not working.
- Additional trouble codes in Trionic (P1901).
- Additional diagnostic trouble codes in the TCM (P1902 or P1923).
- CHECK ENGINE

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.

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

Dependents:
- None.

System reaction to a fault:
- Cruise control is blocked.

OK report:

Fault handling: Fault Handling III, Other Emission-Related Comp. & Function
- Enable criteria fulfilled and fault criteria not fulfilled within 60 s.
- 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