The OnStar® Communication Interface Module (CIM) performs an internal electronic erasable programmable read only memory (EEPROM) checksum as a part of its internal diagnostics as the CIM is initialized on start up. If the check sum does not match the predetermined value, this DTC will fail. If the condition corrects itself on the next power up, the DTC will clear.

If DTC B1009 is current in the CIM, clear DTC using the Scan tool. Cycle the ignition Off. Wait 10 seconds. Cycle ignition On. If DTC B1009 resets as current in OnStar® CIM, replace module.