P0657 Actuator supply voltage: open circuit ("A")

By: Diagno editorial team · Updated: 2026-10-15

P0657 means: Actuator supply voltage: open circuit ("A"). The computer feeds the sensors a 5-volt reference voltage. Drive gently and have the car checked soon. The repair usually costs about €40–400 in Estonia. The most common cause: connector loose, damp or corroded. Other possible causes: wire broken or chafed, faulty sensor.

What it means

The computer feeds the sensors a 5-volt reference voltage. That voltage is missing, too low or too high, so several sensors may read wrong at once. The computer sees no current in the circuit, so something is open: a wire, a connector or the part's winding.

What you may notice

• Several fault codes at once
• Limp mode
• The engine may not start

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or chafed
3. 3Faulty sensor
4. 4Engine computer fault (rare)

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? If several sensor faults appeared together, a shared supply is probably the cause. Check connectors that were recently disturbed. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the sensor

Standard SAE description: Actuator Supply Voltage "A" Circuit/Open