What Does P0659 Mean?
The actuator supply voltage circuit 'A' is reading higher than the maximum threshold. The ECM has detected an over-voltage condition on the actuator power supply line, which can damage actuators (solenoids, motors) by driving them beyond their rated voltage. This is often related to a charging system fault or short to a higher voltage source. The driver may notice harsh actuator operation, buzzing solenoids, or premature actuator failure.
Common Causes
35%
Overcharging alternator producing excessive voltage (regulator failure)
25%
Short to a higher voltage source in the actuator supply wiring
20%
ECM internal voltage monitoring circuit malfunction (false high reading)
15%
Faulty relay allowing unregulated voltage to pass through to actuator supply
5%
Battery terminal voltage spike from poor connections under load
Diagnostic Steps
1
With engine running, measure charging system voltage at the battery terminals. Normal is 13.5-14.7V. If voltage exceeds 15.0V, the alternator voltage regulator is likely failing and is the root cause.
2
Measure the actuator supply 'A' voltage at the ECM connector pin. Compare to battery voltage. If significantly higher than battery voltage, there is a fault in the supply circuit itself (not just charging system).
3
If charging system voltage is normal, inspect the actuator supply wiring for any cross-contact with other circuits. Check for pinched wires, damaged insulation, or incorrect connections from previous repairs.
4
Test the actuator supply relay by swapping it with a known-good relay of the same specification. Measure voltage output of the relay to verify it passes clean battery voltage.
5
If all external circuits test normal, the ECM's internal voltage monitoring reference may have shifted. Try an ECM reflash first before considering replacement.
Estimated Repair Cost
$50 - $700
Parts + labor, varies by vehicle and location
The actuator supply voltage circuit 'A' is reading higher than the maximum threshold. The ECM has detected an over-voltage condition on the actuator power supply line, which can damage actuators (solenoids, motors) by driving them beyond their rated voltage. This is often related to a charging syste...
The most common cause of P0659 (Actuator Supply Voltage "A" Circuit High) is: Overcharging alternator producing excessive voltage (regulator failure)
Typical repair costs for P0659 range from $50 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Over-voltage can damage electronic actuators and modules. If caused by an overcharging alternator, continued driving risks damaging the battery, ECM, and other electronics. If charging voltage is over 15.5V, stop driving and have the alternator tested immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0659 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Engine Actuator Supply / Charging System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
