OnStar Back up Battery Failure - keywords B1446 B1447 battery bulb LED onstar red

This PI was superceded to update update model years. Please discard PIC4541.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Dealers may comment that they are recording DTCs B1446 or B1447 for OnStar® back-up battery failure in the VCIM. The OnStar® status LED will be illuminated red.

Do not disconnect the main vehicle battery or remove the OnStar® fuse with the ignition key in any position other than OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the drivers door should disable RAP) before disconnecting power.

Disconnecting power to the OnStar® module in any way while the ignition is ON or with RAP activated may cause activation of the OnStar® Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. This action is per design as the BUB is designed to provide power to the VCIM so an emergency notification call can be made after a vehicle collision where the main battery is disabled.

Once the Back-Up Battery is activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced. Follow the instructions in eSI for Communication Interface Module Battery Replacement.

Important: Do not remove power from the OnStar® VCIM with the key on or with RAP activated.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.