Circuit Description
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The DTC P0641 5-Volt Reference 1 Circuit diagnostic detects an incorrect voltage on the reference A supply circuit. The powertrain control module (PCM) provides 5 volts to the reference A circuit to the following sensors:
- The accelerator pedal position (APP) sensor 1
- The manifold absolute pressure (MAP) sensor
- The automatic transmission output shaft speed (AT 0SS) sensor
These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a short circuit condition on the 5-volt reference of one sensor can affect the operation of the other sensors. The PCM monitors the voltage on the 5-volt reference circuit. If the PCM detects that the voltage is out of tolerance, DTC P0641 sets.