DTC P0641: 5-Volt Reference Circuit Out Of Range: Description

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Control Module (ECM) provides 5 volts to the following sensors:

The Accelerator Pedal Position (APP) sensor 1.
The APP sensor 3.
The Engine Oil Pressure (EOP) sensor.

These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The ECM monitors the voltage on the 5-volt reference circuit. If the ECM detects that the voltage is out of tolerance, DTC P0641 sets.