What does code P1637 mean?

Q: What does code P1637 mean?

Alternator Warning Lamp Control Signal. P1637 on a GM vehicle means the engine control module (ECM) has detected a fault in the control circuit for the alternator warning lamp, which is the battery symbol in the instrument cluster. The ECM monitors the voltage or current on this circuit and sets the code when the signal does not match the expected state, often because the lamp circuit is open, shorted, or the cluster is not responding.

DTC codes / GM codes / P1637

P1637 · GMAlternator Warning Lamp Control Signal

P1637 on a GM vehicle means the engine control module (ECM) has detected a fault in the control circuit for the alternator warning lamp, which is the battery symbol in the instrument cluster. The ECM monitors the voltage or current on this circuit and sets the code when the signal does not match the expected state, often because the lamp circuit is open, shorted, or the cluster is not responding.

SystemPowertrain

Code typeGM specific

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.