P0629 code: Fuel Pump A Control Circuit High
P0629 means fuel Pump A Control Circuit High. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0629 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.
P0629 symptoms
- 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 P0629
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 →
How to fix P0629
Moderate — doable at home with common tools and patience
- Check whether the pump runs after shut-off
Switch the engine off, let the ignition fully power down, and listen at the filler neck or tank area. A pump that keeps humming, or a battery found flat after sitting, means something is holding the circuit on — a strong pointer toward a stuck relay or a control wire shorted to power.
- Pull the relay and see if the pump stops
With the pump running when it shouldn't, remove the fuel pump relay. If it stops, either the contacts have welded shut or the control wire is being powered; fit a new relay and retest. If it keeps running with the relay out, power is reaching the pump another way, such as a chafed wire or a faulty driver module.
- Test the control wire for unwanted voltage
With the relay or module and the computer connector unplugged, turn the key on and measure the control wire to ground. It should read zero; any voltage means it is shorted to a powered circuit. Look where it runs beside other live wires — under carpet, along the frame, or at the rear harness near trailer wiring.
- Look for aftermarket wiring in the circuit
Remote starters, alarms, and fuel-cut immobilizers are often spliced into the pump circuit, and a backfeed from one can hold the control line high. Trace any non-factory splices, connectors, or tape near the fuse box or relay, and retest with the add-on disconnected; a code that disappears points straight at the install.
- Check the driver module and its ground
On returnless systems, inspect the pump driver module's connector and ground for corrosion, and if your scan tool shows it, compare commanded pump duty with what the module reports. A module reporting stuck high with good wiring is faulty; a fault in the engine computer itself is rare and needs a shop with programming.
DIY or shop? Listening for a run-on pump, pulling the relay, and checking the control wire for voltage are quick tests most owners can manage with a multimeter, and driver modules are frequently bolt-on parts. Get a shop involved if the short is buried in the harness, if a remote start or alarm install needs untangling, or if testing points at the engine computer. Until it's fixed, a pump that won't switch off can flatten the battery, so consider disconnecting it if the car will sit.
Tools for the DIY steps: Digital multimeter · Test light · Spare fuel pump relay · Wiring diagram for the pump circuit · Scan tool with live data
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0629.
Start a case with P0629 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0629?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0629: common questions
Can I drive with P0629?
A code alone can't settle that. 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, and stop driving if the car stalls.
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.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0629 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0629 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.