Circuit Description
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix, 2002 Chevrolet Malibu, and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The PCM uses the 5-volt reference 1 circuit as a sensor feed to the TP sensor, MAP sensor, EGR valve pintle position sensor and the FTP sensor.
The PCM monitors the voltage on the 5-volt reference 1 circuit. If voltage is out of tolerance, PCM will set DTC P1635.