equipment. Anytime aftermarket accessories are installed into the courtesy lamp circuit, it
can cause the inadvertent power timer in the body control module (BCM) to keep resetting.
This would cause the BCM to remain awake and cause a current drain on the battery.
Customer driving habits, such as regular short trips. This does not allow enough time to
properly charge the battery. Refer to Battery Description and Operation.
Verify that the battery and charging system are in proper working order. Refer to Battery
Charging and Charging System Test.
A battery discharging for no apparent reason while the vehicle is parked can be caused by
an intermittent draw, such as a module waking up, or a continuous draw, such as a dome
light or stuck relay. Look and listen for any components that may be operating when they
should turn off, such as a fuel pump.
Some systems and modules such as OnStar®, and regulated voltage control (RVC), if
equipped, are designed to wake-up, perform a task, and go back asleep at regular intervals.
Refer to Body Control System Description and Operation for the system or modules
description and operation.
Remote keyless entry (RKE) will wake up due to an outside input. Refer to Keyless Entry
System Description and Operation for the system description and operation.
The battery run down time will vary depending on cold cranking amperage (CCA) and
reserve capacity (RC). If the CCA and RC are higher, then the battery run down time would
be longer. If the CCA and RC are lower, then the battery run down time would be shorter.
The graph below indicates roughly how many days a 690 CCA battery with at 110 min. RC
(60.5 AH) starting at 80 percent state of charge will last with a constant current draw until it
reaches 50 percent state of charge. Differences in battery rating and temperature will affect
the results.
IMPORTANT: The battery specification listed below is a generic
specification. Refer to Battery Usage when testing the
battery.
Current Drain
Days
25 mA
30.5
50 mA
16.5
75 mA
11
100 mA
8.25
250 mA
3.3
500 mA
1.65
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Electrical - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado