Conditions

Vehicle Speed. No input signal.





Fault symptoms
- CHECK ENGINE.
- Cruise control not working.
- Low engine torque on cars with manual gearbox.

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. Engine speed above 1750 rpm. Load above 480 mg/c. Brake pedal not depressed. Coolant temperature exceeds 60 °C.

Fault criteria:
- No vehicle speed for more than 5 s.

Then, 17 minutes without the vehicle speed leaving 0. On automatic cars, the selector lever must also have another value than P or N. Enable criteria for these two fault criteria need not be fulfilled.

Dependents:
- P1576 and P1577.

System reaction to a fault:
- Cruise control is blocked. Vehicle speed (Bus from MIU) is used as a substitute value. The idling adaptation is blocked and reset.

OK report:
- 60 s has expired since start. Vehicle speed has exceeded 0 on some occasion.

Diagnostic help
Fault diagnosis concerns electrical faults in connecting leads to ABS (First it is checked if there are faults in the ABS or TC/ABS). If the car is equipped with TC/ABS the communication to the Trionic occurs through the P-bus. For further information about communication with TC/ABS,

If TC/ABS is absent on the bus,

Functions in the diagnostic tool related to the fault:
- Diagnostic status for the diagnosis.
- Vehicle speed (Leads from ABS, alternatively bus from TC/ABS.), unit km/h.

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.

Proceed to Diagnostic Procedures Checking Diagnostic Trouble Codes In the ABS