P067A: cylinder 4 glow ground-short and inrush-current assessment

P067A checks cylinder 4's glow output for a ground-short condition. The cited strategy includes a low-impedance detection case and an excessive-inrush-current case.

The initial current event can matter

The inrush-profile assessment occurs once per driving cycle at key-on. A normal-looking circuit later in the drive does not establish that its initial current behavior was acceptable. Retaining whether the fault followed initial activation is useful diagnostic context, although it does not identify the physical cause.

The impedance description specifies ground-short detection at 0.11 ohm and no such detection above 0.19 ohm. These values characterize the hardware fault test; they are not a complete healthy-plug resistance band.

Normal monitoring has its own gates

The ordinary check requires a running engine outside cranking, valid battery voltage, no glow-supply fault, enabled diagnostics and duty cycle above 2.50% but below 97.50%. Ten failures among twenty 100 ms samples meet the listed filter, with Type B reporting and glow-lamp indication.

Verification should address the relevant initial or operating event on the correctly identified cylinder-4 channel. The summary does not isolate the element from its wiring and driver or prove that a plug replacement is necessary. It also provides no direct-power test or instruction to bypass glow-system current protection; use the applicable professional service procedure.

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 1244.