P0C4F: Motor B learning can fail by range or by a sudden change

P0C4F checks the result of motor-B resolver-offset learning in this GM table. A completed learn can fail in two ways: its absolute correction exceeds 30 degrees, or its correction differs from the previously stored value by more than 10 degrees. The second branch makes prior learning history diagnostically important.

Keep the previous value when available

A correction may remain inside the absolute 30-degree limit yet still differ too much from the earlier stored result. Treating the code only as an absolute-angle failure can therefore overlook the branch that actually explains the event.

Both comparisons require a completed learn. The listed conditions include motor speed below 20 rpm and high-voltage supply above 192 volts, with a 300-millisecond learn time. An aborted or never-completed procedure is a different kind of evidence.

Do not turn the result into a parts diagnosis

Retain the prior correction, new correction, completion status and relevant position-sensing faults for the trained technician. The monitor does not by itself identify an incorrect mechanical assembly, a failed sensor or a required replacement motor.

This is a historical motor-B controller calibration. The table does not map B to a universal physical drive unit or establish a safe manual learning method. The exact vehicle service procedure must control resolver learning and high-voltage work. Verification should explain which of the two documented branches was resolved, rather than merely note that memory was cleared.

Source and applicability

15OBDG01 Hybrid Diagnostics, cited controller and monitor only. Historical calibration limits are not universal specifications; per-code vehicle, engine and hardware applicability must be verified.

GM source, physical page 687.