P1635 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC: 5-VOLT REFERENCE CIRCUIT LOW CONDITIONS
POST UPDATED IN January, 2023
P1635 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC: 5-VOLT REFERENCE CIRCUIT LOW CONDITIONS
The PCM (Powertrain Control Module), as the engine management module, monitors and ensures the right performance of all the systems under its charge. This controller uses a common 5-volt reference circuit as the sensor power supply. This circuit delivers 5 volts to the Air Conditioning (A/C) Pressure Sensor, Exhaust Gas Recirculation Valve (EGR), and Manifold Absolute Pressure (MAP) Sensor. The PCM continuously monitors the voltage of the 5-volt reference circuit 1.
If the sensor reference voltage is out of range, the PCM will set the P1635 OBD2 fault code.
Reasons for setting the P1635 OBDII diagnostic code:
Steps to troubleshoot the OBD2 DTC P1635: