DTC P1635: 5-Volt Reference 1 Circuit: Description
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Control Module (ECM) uses the 5-volt reference 1 circuit as a sensor feed to the following sensors:
- The Accelerator Pedal Position (APP) sensor 1.
- The APP sensor 3.
- The Fuel Rail Pressure (FRP) sensor.
The ECM monitors the voltage on the 5-volt reference 1 circuit. If the voltage is out of tolerance, the ECM will set DTC P1635.