P1635 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC: 5-VOLT REFERENCE CIRCUIT LOW CONDITIONS
POST UPDATED IN January, 2023
P1635 Code failures by brands
Description of DTC code P1635
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.
Symptoms of fault code P1635
- Check Engine light illuminated.
Causes of OBD2 P1635
Reasons for setting the P1635 OBDII diagnostic code:
- The A/C Pressure Sensor wires or connectors may be damaged.
- The MAP Sensor circuit may have deficiencies that cause a short or open circuit.
- The EGR Valve wiring may have defects that cause the malfunction.
Possible solutions of the DTC code P1635
Steps to troubleshoot the OBD2 DTC P1635:
- Consult the Technical Service Bulletins. These contain useful information provided directly by the manufacturer.
- Use an automotive scanner to check if any other trouble codes in addition to the P1635 are stored. If so, these need to be diagnosed in the order listed on the tool.
- Check the wiring and connectors that relate to the A/C Pressure Sensor, MAP Sensor, and EGR Valve. Look for common damage that could cause a short in the circuit. Repair or replace if necessary.
