OBD codes / P0629
P0629
SeriousFuel Pump A Control Circuit High
Like the other fuel pump control codes, P0629 can end in a stall or a no-start, and a pump that never shuts off can also flatten your battery overnight. Keep trips short, listen for the pump running after key-off, and get the circuit diagnosed promptly.
What this code means
P0629 is the mirror image of P0628: the voltage on the fuel pump control circuit is stuck higher than the computer expects. Typical causes are a control wire shorted to battery voltage, a relay stuck closed, a corroded connector, or a failing fuel pump driver module. A circuit stuck high can mean the computer has lost the ability to switch the pump properly — in some cases the pump runs constantly (even after key-off, draining the battery), and in others the system shuts the pump down as a fail-safe, causing stalling or a no-start. Either way it's a wiring-and-electronics diagnosis, with the relay as the cheap first suspect and the driver module and harness as the deeper checks.
Symptoms you might notice
- Engine cranks but won't start, or stalls
- Fuel pump audibly running after the key is off
- Battery draining overnight
- Hard starting or hesitation
- Check-engine light
What it costs to fix
Typical range: $20–$600 · about ~0.2–2 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Fuel pump relay | $15–$50 | ~0.2–0.5 hrs |
| Wiring / connector repair | $5–$100 | ~0.5–2 hrs |
| Fuel pump driver module (where fitted) | $100–$400 | ~0.5–1.5 hrs |
A stuck relay is the cheap and satisfying fix; a short to power in the harness takes tracing time; a driver module is the pricier part. The spread is wide because the code names the circuit, not the component — testing tells you which end of the range you're on.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0629 for my exact vehicle →
Frequently asked
Can I drive with P0629?
Briefly and carefully. The system controlling your fuel pump isn't switching correctly, and stalling or a no-start is the realistic failure mode. Have it diagnosed soon.
Why is my battery dead in the morning with this code?
If the relay is stuck closed or the control wire is shorted to power, the fuel pump can keep running after you shut the car off, quietly draining the battery. If you can hear a hum from the tank area with the key off, that's the confirmation.
What's the difference between P0628 and P0629?
P0628 means the control circuit reads lower than expected; P0629 means higher. They share suspects — relay, wiring, driver module — but point the electrical diagnosis in opposite directions (short to ground versus short to power).
Is this an expensive fix?
Often not — a relay is cheap and a common cause. Wiring repairs are moderate, and the fuel pump driver module is the more expensive electronic part. It has to be tested rather than guessed to avoid replacing the wrong thing.
Seeing P0629 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0629 for my vehicleRelated trouble codes
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Generic OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.