For 1990-2009 cars

### Circuit Description

The OnStar® Communication Interface Module (CIM) performs an internal diagnostic check on the keep alive memory portion of the CIM. If the test results in an error, DTC B1004 will fail. This DTC could fail as current or history. If B1004 is current the corruption of keep alive memory exist.

### Conditions for Setting the DTC

• | Keep Alive Memory (KAM) internal diagnostic error.

• | This DTC will fail if power and/or ground to the CIM are lost.

• | B1004 will run once per ignition cycle.

• | Illuminate the red OnStar® LED

### Diagnostic Aids

If the DTC is current a serious memory problem exists replace the CIM.

This DTC will usually fail and become a history code. If DTC B1004 is in history check for history communication DTCs in the BCM. You must diagnose the communication DTCs first. A lost communication DTC in the BCM points to a lost power or ground for the OnStar® CIM.