What it means
Same as P0657 with the supply voltage above the plausible range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Actuator supply voltage A powers a group of engine actuators, which can include injectors, throttle, or EGR components depending on the vehicle. P0659 sets when the control module detects that this supply is above its expected range, which can stress or disrupt the actuators connected to it.
Common causes
Most likely first.
- Supply voltage above design range
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Read freeze-frame data and scan for related actuator codes to identify which systems share supply A.
- Monitor actuator supply voltage and engine live data to confirm the high condition and whether it changes with engine speed or electrical load.
- Inspect supply A wiring and connectors for pinched insulation, a loose terminal, corrosion, or contact with a higher-voltage wire.
- Check charging-system voltage and the supply circuit for an unintended connection to battery voltage, using the wiring diagram and manufacturer's specification.
- If the wiring is sound, test the relay and control module output to determine where the excessive voltage originates.
Common fixes
- Repair wiring where supply A is shorted to a higher-voltage source.
- Replace damaged or pinched harness sections and secure them away from power wiring.
- Repair a faulty relay or connector identified by testing.
- Repair the control module output only if the external supply circuit checks out.
Can I keep driving?
Excessive actuator supply voltage can cause erratic engine operation or damage connected components. Limit driving if the engine runs poorly or warning lights multiply, and have the supply fault corrected promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.