P05CE: Exhaust cam error during catalyst warmup needs its own timing window

P05CE identifies cold-start exhaust camshaft timing performance on bank 1. The cited GM strategy evaluates position error when the cold-start phaser positions are being commanded, rather than judging every exhaust cam movement throughout the drive.

Command stability determines whether the comparison is useful

The monitor compares the absolute difference between desired and actual cam position with a six-degree limit. Both positions must be inside the documented six-to-thirty-two-degree operating window. The desired position must have varied by less than three degrees for a calibration-defined interval before the comparison qualifies.

Exhaust phaser enablement, a running engine and catalyst warmup are required. Supply must exceed 11 V and power take-off operation must be inactive. Existing exhaust actuator circuit faults can inhibit the test, so a missing performance result during such a fault is not proof that timing control passed.

Verify the original cold-start condition

The table uses sixty-five failed samples within seventy-five, sampled at 100-millisecond intervals, with two-trip reporting. A useful record retains the warmup phase, requested angle, measured angle and command-stability state together.

If timing follows normally once warmup has ended, that observation does not reproduce this particular test. Likewise, a deviation during an intentionally changing request may fall outside its stated comparison window. The monitor supports investigation of eligible target-tracking error; it does not identify a particular exhaust phaser, oil path or mechanical timing component as the cause without further service checks.

Source and applicability

2025 GM 03B documented monitor only. Vehicle, engine and controller calibration applicability must be established separately; no model fitment is inferred from the file. GM PDF, physical page 519.