Conditions for Setting the DTC
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
P0850 or P0851
The ECM detects the Park/Neutral switch signal equals 0 volts, Low, when the IMS reports a Drive range.
P0852
The ECM detects the Park/Neutral switch signal equals 12 volts, High, when the IMS reports a Park/Neutral range.