This bulletin applies to 2018 and prior Chevy Express H1500 vehicles. Some customers may comment about an intermittent MIL being illuminated with a message that displays “reduced engine power.” This condition may be caused by water intrusion into the instrument panel to the body harness connector, which carries the APP sensor signals to the ECM/PCM. This water intrusion results in a voltage difference between APP sensor 1 and APP sensor 2 that exceeds a predetermined value for more than a calibrated period of time, setting DTC P2138.
Note that aftermarket equipment can potentially generate this same code. Verify that aftermarket equipment is not electrically connected to any of the APP sensor signal or low reference circuits or to any other ECM/PCM 5V reference or low reference circuits.
Inspect for a water leak in the area and repair as needed.