P067F: cylinder 6 glow-plug output high-circuit fault

The cylinder 6 glow-plug circuit is the subject of P067F in the reviewed 2025 GM monitor. The controller checks its electrical integrity and recognizes an output connection toward a voltage source. A high-circuit code alone does not identify whether the defect lies in the plug, its connection or the control circuitry.

The source defines two electrical cases

For load resistance greater than 0.65 ohm, the short-to-power criterion uses impedance below 0.5 ohm to a source within the normal or high operating-voltage range. When load resistance is between 0.2 and 0.65 ohm, the limit is below 0.14 ohm instead.

Those alternative limits explain why a generic “check for high resistance” interpretation is misleading. The monitored fault is a low-impedance route toward voltage, evaluated in relation to load resistance. A removed component's resistance is a different measurement.

Conditions that affect verification

GM requires the engine to be running but not cranking, acceptable battery voltage, no glow-system supply fault, calibration enablement and an enabled diagnostic system. The counter needs 10 failing samples within 20, with a 100-millisecond task interval. The listed reporting class is Type B over two trips, accompanied by glow-lamp activation.

If supply faults remain active, absence of a fresh P067F may reflect an inhibited check. Confirm that the relevant conditions were satisfied before evaluating a repair. These facts are bounded to the published monitor; they do not establish every model using the code or provide a safe circuit-probing procedure.

Source: GM monitor, PDF page 1249.