P0658: shared actuator supply is checked while switched on

P0658 is actuator supply circuit low in the generic dictionary. The cited ECM implementation is more specific: shared high-side driver 1, restricted by the source to GEN III controllers. Its monitor looks for a ground-short signature while the output is powered on.

A shared supply is not one named actuator

The row does not identify every device connected to that high-side supply. Multiple actuator complaints may justify checking their actual supply mapping, but this code alone cannot assign the failure to any particular actuator. The architecture restriction also prevents transferring this exact monitor to an unidentified controller generation.

The detection specification describes less than 0.5 ohm between the output and controller ground. Actual driver voltage thresholds are controller specific. This is not an instruction to measure resistance on a powered shared supply.

Enabling and verification

The powertrain relay must be on, its voltage at least 11 volts, and run/crank voltage above 5 volts. The controller uses twenty failed samples out of twenty-five at one hundred milliseconds per sample. An off-state reading or low supply outside those prerequisites does not recreate the defined failure condition.

Record supply command and relay state alongside the diagnostic result. A repair should be verified with the high-side output active and the relevant monitor passing under suitable voltage conditions. The table lists Type A over one trip and does not authorize bypassing the shared driver or replacing the module without the vehicle-specific circuit diagnosis.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 416.