P0C57: motor B resolver circuit A low evaluates the S13 reference

P0C57 is motor B position-sensor circuit A low in the cited GM table. The source identifies the measured quantity as the resolver S13 circuit reference voltage. It is an electrical-range diagnosis, not a direct determination that the motor's angular position is mechanically incorrect.

Reconstruct the low-range event

The threshold is reference voltage below 0.5 V with the wakeup signal on. GM uses fifty qualifying counts out of eighty at a 10.4 ms rate and lists one-trip reporting. A single transient scan value is therefore different from the filtered event used by the controller.

The adjacent high-range branch uses a different threshold and count requirement. Preserve the original direction and code status rather than treating all resolver reference faults as one interchangeable condition.

Keep learning status separate

The document also defines a motor B not-learned diagnosis. A low reference fault does not alone prove that a learned offset needs mechanical correction. Record related circuit and learning faults to determine which tests were meaningful during the original event.

The parameter table supplies no universal S13 pinout, component replacement or safe probing method. The vehicle-specific hybrid circuit procedure must establish the actual signal path and cause. A qualified technician should verify credible reference-voltage behavior under eligible operation, with proper high-voltage isolation before any physical inverter or motor work.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, cited BPCM or hybrid-controller monitor only. Historical calibration values are not universal specifications; no per-code model, engine or hardware fitment has been established. GM PDF, physical page 304.