Back-up Battery (If Equipped)
Do not disconnect the main vehicle battery or remove the telematics communication interface control module fuse with the ignition key in any position other than OFF. Disconnecting power to the telematics communication interface control module in any way while the ignition is ON or with retained accessory power activated may cause activation of the OnStar® Back-Up Battery. This action is per design as the back-up battery is designed to provide power to the vehicle communication interface module 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 back-up battery is not rechargeable and once activated the back-up battery must be replaced.
Certain OnStar® equipped vehicles may also be equipped with a back-up battery. The back-up battery is a non-rechargeable, lithium battery intended to provide an auxiliary power source for the vehicle communication interface module in the event of a vehicle collision where power from the main vehicle battery is lost.
The back-up battery is intended to have a limited life span of approximately 4 years and is designed to maintain an open circuit voltage between 16 V and 9 V throughout this period. This allows the battery to power the basic functions of the vehicle communication interface module 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 back-up battery is connected to the vehicle communication interface module 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 back-up battery positive voltage circuit is shorted to the back-up battery 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 vehicle communication interface module.