P0657Actuator Supply Voltage A Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Actuator supply A is a high-side switch feeding several actuators together; its use differs by maker (Ford transmission solenoids, GM shared high-side driver, GM Europe 2.0 CDTI internal 5 V supply). P0657 is the open-circuit code; it is documented at Ford: the high-side switch of the 5R110W and 6R80 automatics feeds all shift solenoids, and the 2023 diesels split them into two supplies (P0657 and P2669), checked continuously. On a fault the solenoids are de-energised and the transmission falls back to a mechanical limp gear with maximum line pressure – harsh shifts and a single forward gear. Ford's 6.8 L V10 reports it with or without the lamp depending on the variant. GM does not use P0657 and reports opens together with ground faults under P0658.
- What you may notice
- Transmission limp mode (fixed gear)
- Harsh shifts, no upshift
- Check engine light (depending on the variant)
- Codes for individual shift solenoids
- Likely causes
- LikelyOpen or connector fault at the transmission pass-through connector or wire to the valve body
- PossibleDamaged harness
- PossibleInternal high-side switch in the engine or transmission module
- RareInternal transmission harness
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.