For 1990-2009 cars

### Circuit Description

The OnStar® Communication Interface Module (CIM) performs an internal diagnostic function that monitors many functions internal to the CIM. If one or more diagnostics do not pass then this DTC will fail.

### Conditions for Setting the DTC

• | Internal diagnostic function.

• | Illuminate the red OnStar® LED.

• | This diagnostic runs once every 300 ms with key on.

### Diagnostic Aids

If this DTC exists with other DTCs, repair the other DTCs first. Refer to appropriate DTC table in this section. Clear DTCs and then turn Off ignition and back On. Check to see if B1000 sets again.