Back-up Battery (BUB) (If Equipped)

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: Do not disconnect the main vehicle battery or remove the OnStar® fuse with the ignition key in any position other than OFF. 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). This action is per design as the BUB is designed to provide power to the CIM 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.

Certain OnStar® equipped vehicles may also be equipped with a back-up battery (BUB). The BUB is a non-rechargeable, lithium battery intended to provide an auxiliary power source for the communication interface module (CIM) in the event of a vehicle collision where power from the main vehicle battery is lost.

The BUB is intended to have a limited life span of approximately 4 years and is designed to maintain an open circuit voltage between 16V and 9V throughout this period. This allows the battery to power the basic functions of the CIM for least one 200 second (5 minute) call at the end of the 4 year span, should a main vehicle battery loss collision occur.

The BUB is connected to the CIM through the back-up battery positive voltage circuit and back-up battery ground circuit and is protected from a short circuit by means of an internal fuse. In the event the BUB battery positive voltage circuit is shorted to the BUB ground circuit or chassis ground, the fuse will open and render the back-up battery permanently inoperable. The status of the back-up battery and its associated wiring is monitored by the CIM.