P037E: glow-system sense feedback relative to supply voltage

P037E checks glow-system electrical feedback during operation in the cited GM strategy. The threshold expression compares battery voltage minus feedback voltage with a calibrated maximum difference that depends on system current.

A differential check, not a universal low-voltage number

The table does not publish a single numeric low-feedback threshold. Its explicit expression makes supply voltage and current part of the interpretation, so judging the sense value without those quantities loses essential context.

There is also a wording conflict: the malfunction prose says feedback is “above” a threshold, while the code is circuit low and the threshold column uses the battery-minus-feedback difference. The supported differential expression is reported here; a vehicle-specific definition must resolve that prose inconsistency before pin-level diagnosis.

Enable conditions narrow the conclusion

The check requires key-on engine operation excluding cranking, battery voltage in range, glow enable active and no listed glow-plug electrical or glow-supply fault. It uses 60 failed samples among 120 on a 50 ms task, with Type B, two-trip reporting.

Consequently, a cranking observation or a test with a separate supply fault does not reproduce this monitor. Verification should capture valid sense feedback relative to supply during an enabled glow event. Although the strategy mentions an ECU internal fault, this summary alone cannot justify controller replacement or bypassing glow-system protection.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1178.