P1637 BUICK, CADILLAC, CHEVROLET, GMC: GENERATOR L-TERMINAL CIRCUIT
POST UPDATED IN February, 2023
P1637 BUICK, CADILLAC, CHEVROLET, GMC: GENERATOR L-TERMINAL CIRCUIT
The generator L-terminal circuit is discrete, i.e. this circuit has no junctions and only one source and one destination in the PCM (Powertrain Control Module). This controller applies the ignition voltage to the generator L-terminal circuit. A small amount of voltage flows from this circuit through the generator windings to create a magnetic field that starts the generator process. When the generator is at operating speed and producing voltage, the solid-state switch for the generator’s L-terminal circuit opens. The PCM senses that the initial starting current flow has stopped.
The PCM expects to detect low voltage on the L-terminal circuit before the generator turns to operate speed. Conversely, expects the circuit to be at ignition voltage potential when the generator is running. If the PCM detects a fault (short or open circuit), the diagnostic code P1637 OBDII will be set.
DTC P1637 OBD2 is set for one of the following reasons:
If you have no knowledge of mechanics, it is recommended that you go urgently to the nearest garage in your area. A professional in the field will be able to detect and solve this code without any problems. On the other hand, if you have the necessary knowledge to repair this code, you can follow these possible solutions to troubleshoot the P1637 OBDII fault code: