DTC P1639: 5-Volt Reference B Circuit: Description
WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) provides a 5-volt reference to the following sensors:
- The Throttle Position (TP) sensor 2.
- The Accelerator Pedal Position (APP) sensor 1.
- The manifold absolute pressure (MAP) sensor.