Amplifier Speaker Outputs
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
At a low volume, the plus (+) and minus (-) speaker outputs circuits measure approximately 2-7V AC or 7-8V DC at the speaker connector when testing a normal working system. If a plus or minus for any speaker output is shorted to ground or voltage, the amplifier circuitry will turn OFF the front outputs or rear outputs for component protection. In addition, the GMLAN amplifier sets a DTC for the affected speaker output circuit.