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P codepowertrainMedium severity

P0658Actuator Supply Voltage "A" Circuit Low

The actuator supply voltage "A" circuit from the PCM is stuck low, usually meaning the feed is shorted to ground or the supply has collapsed under load.

Definition

The PCM monitors the switched supply voltage it delivers to its "A" actuator group and sets P0658 when that circuit voltage stays below the expected threshold while commanded on. A short to ground on the supply or inside one of the powered actuators pulls the whole feed down, so the affected devices — often the throttle actuator or transmission and emissions solenoids — stop working together. Expect the MIL, reduced engine power or limp-home transmission behavior, and possibly a repeatedly blowing fuse if the short is direct.

Common causes

  • Supply wire chafed through and shorted to ground in the engine or transmission harness
  • Internally shorted actuator or solenoid dragging down the shared supply
  • Blown fuse from a transient short leaving the circuit at 0 volts
  • Water intrusion in a connector creating a path to ground
  • Harness pinched during recent engine or transmission service
  • Failed PCM supply driver (rare)

Common misdiagnoses

  • Replacing the PCM before locating a harness or component short
  • Throttle body replaced when a different device on the shared supply is shorted
  • Repeated fuse replacement without finding the ground fault
  • Transmission overhauled for solenoid codes caused by the dead supply

Troubleshooting steps

  1. 1.Check the supply fuse first

    A blown actuator-supply fuse confirms a hard short; replace it only after locating the fault, or use a fused jumper or short-finder to trace it.

  2. 2.Measure the supply voltage

    Backprobe the supply circuit key-on; near 0 volts while commanded on confirms the circuit is shorted or the driver is off.

  3. 3.Unload the circuit device by device

    Disconnect each actuator fed by supply "A" one at a time; if the voltage recovers when one is unplugged, that component is internally shorted.

  4. 4.Ohm the harness to ground

    With the PCM and all actuators disconnected, measure the supply wire to ground — any reading other than open indicates a harness short, commonly at chafe points over brackets or near the exhaust.

  5. 5.Repair and confirm under load

    After the repair, verify the supply holds battery voltage with all actuators connected and operating, then clear codes and road test for reduced-power recurrence.

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