WARNING: This page is about a different car, the 2009 GMC Sierra and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Circuit
Short to Ground
Open/High Resistance
Short to Voltage
Signal Performance
Battery Positive Voltage
P0A8D*
P0AFF**
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* DTC while APM is charging. **DTC with APM prior to charging.