Motor Vehicle Expert
OBD fuel pump high control circuit guide

P0629 Code Meaning UK

P0629 means “Fuel Pump A Control Circuit High”. In plain English, the ECU or PCM has detected a higher-than-expected voltage signal in the fuel pump control circuit. This can cause fuel pump control problems, hard starting, poor acceleration, cutting out, fuel pressure issues, limp mode or a car that cranks but will not start.

📅 Updated June 2026 🇬🇧 UK diagnostic guide 🛠 Fuel pump high circuit advice
Quick answer Diagnosis steps Fault Codes Hub
✓ Fuel pump high circuit explained ✓ Can you drive advice ✓ UK repair cost guide ✓ Vehicles affected included
Quick answer Meaning Symptoms Causes Severity Can you drive? Repair costs Diagnosis Vehicles affected Common mistakes MOT impact Used car advice Related guides FAQs
Quick answer

What does P0629 mean?

P0629 means the fuel pump A control circuit is reading high. The ECU expects a normal voltage or response from the fuel pump control circuit, but the signal is higher than it should be.

This can happen if the pump control wire is shorted to power, the fuel pump relay sticks, the fuel pump control module fails, the wiring has been damaged, the connector is corroded, or the ECU is seeing an unexpected voltage return from the fuel pump circuit.

P0629 is important because the fuel pump circuit controls fuel delivery. If the pump is not controlled correctly, the car may hesitate, lose power, cut out, crank but not start or suffer unstable fuel pressure.

Most important first check

Check fuel pump relay, fuse, control module, pump command, voltage at the pump, ground and wiring shorts.

Main risk

High circuit voltage can cause wrong pump control, unstable pressure, cutting out or no-start.

Best next step

Test the fuel pump control circuit and fuel pressure before replacing the pump.

Back to Fault Codes Hub Car Won’t Start Diagnosis
Fault code meaning

P0629 — Fuel Pump A Control Circuit High

The fuel pump control circuit allows the ECU, fuel pump relay or fuel pump control module to control fuel pump operation. The system may simply switch the pump on and off, or it may vary pump speed and pressure depending on engine demand.

When P0629 appears, the ECU has detected a high signal in that circuit. This may mean a short to battery voltage, stuck relay, faulty fuel pump control module, wiring issue, wrong voltage feedback or ECU monitoring fault.

P0629 is closely related to P0628 fuel pump A control circuit low and P0627 fuel pump A control circuit open. P0629 is the high-voltage side of the same fuel pump control circuit fault family.

Mechanic view

Why P0629 needs proper circuit testing

I would not replace the fuel pump just because P0629 is stored. I would first check whether the fuel pump relay is stuck, whether the control wire is shorted to power and whether the pump module is being commanded correctly.

A high circuit fault can be electrical rather than mechanical. A pump can be good but controlled wrongly because of a relay, module or wiring issue. Equally, a faulty pump module can send the wrong feedback and trigger the code.

This is why P0629 links naturally with car cranks but won’t start, car won’t start diagnosis, car losing power when accelerating, P0171 system too lean, P0300 random misfire and the main OBD fault codes hub.

Symptoms

Common symptoms of a P0629 code

P0629 symptoms usually relate to fuel pump control, fuel pressure and engine starting or running problems.

Engine cranks but won’t start

The starter may turn the engine, but the engine may not fire if fuel pump control is wrong.

Engine cuts out

The car may stall if the pump circuit behaves incorrectly while driving.

Hard starting

The engine may take longer to start if fuel pressure is unstable.

Poor acceleration

Fuel pressure problems can cause hesitation, flat spots or weak throttle response.

Losing power under load

The vehicle may struggle uphill, when overtaking or under heavy acceleration.

Engine management light

The engine warning light may appear with P0629 and related fuel delivery faults.

Rough running

The engine may run unevenly if fuel pressure is not stable.

Intermittent no-start

A relay or wiring fault may allow the car to start sometimes and fail other times.

Related lean or misfire codes

Low or unstable fuel pressure may trigger lean running or misfire codes.

Common causes

What causes P0629?

P0629 is normally caused by high voltage, short-to-power, relay, control module, wiring or ECU monitoring problems in the fuel pump control circuit.

Relay

Stuck fuel pump relay

A relay stuck closed can keep the circuit live when it should not be.

Short

Short to battery voltage

Damaged wiring may allow battery voltage onto the pump control circuit.

Module

Fuel pump control module fault

A pump module may command or report the wrong voltage signal.

Wiring

Fuel pump wiring fault

Poor repairs, trapped wiring, water damage or loom damage can trigger high circuit readings.

Connector

Corroded connector

Moisture, loose pins or corrosion near the tank, relay box or control module can affect the circuit.

Pump

Fuel pump internal fault

A failing pump can sometimes affect circuit feedback or current draw.

Fusebox

Fusebox or relay box issue

Heat damage or internal cross-feed can cause unexpected voltage on the circuit.

ECU

ECU control issue

Less commonly, the ECU may command or monitor the pump circuit incorrectly.

Security

Immobiliser or crash cut-off issue

Some vehicles may disable or interrupt pump control after security or impact events.

Severity

How serious is P0629?

Low

Code stored only, engine starts normally, fuel pressure is correct and no drivability symptoms.

Medium

Intermittent hard starting, hesitation, related lean/misfire codes or intermittent pump control fault.

High

No-start, cutting out, unstable fuel pressure, stuck relay, stalling or fuel pump control circuit live when it should not be.

Can you drive?

Can you drive with P0629?

You should only drive with P0629 if the car starts normally, runs smoothly and fuel pressure is confirmed correct. In that situation, a short journey to a garage may be possible.

Do not drive normally if the engine cuts out, cranks but will not start, loses power badly, hesitates under load or has unstable fuel pressure. A fuel pump control fault can leave you stranded suddenly.

✅ Safe for short garage trip: starts normally, no cutting out, no hesitation and fuel pressure is correct.

⚠️ Diagnose soon: intermittent hard starting, stored P0629, occasional hesitation or related lean codes.

🚫 Recovery may be needed: no-start, pump stuck on/off, stalling, unstable fuel pressure or cutting out while driving.

Cranks But Won’t Start Losing Power When Accelerating
Mechanic warning

High pump circuit faults need careful testing

A high control circuit fault can mean the fuel pump control signal is live when it should not be, or the ECU is seeing unexpected voltage from the circuit.

If P0629 appears with P0628, P0627, P0171 or P0300, test fuel pressure and pump control before long journeys.

P0628 Circuit Low P0627 Circuit Open Diagnostic App
Typical UK repair costs

How much does P0629 cost to fix?

Costs vary by vehicle, pump location, wiring access and local labour rate. These are realistic UK guide prices.

Diagnostic scan and fuel pump test

Typical range: £60–£150.

Fuel pressure test

Typical range: £60–£150+.

Fuel pump relay or fuse repair

Typical range: £20–£150+.

Fuel pump wiring repair

Typical range: £80–£400+ depending on access.

Fuel pump connector repair

Typical range: £80–£300+.

Fuel pump control module

Typical range: £150–£600+.

Fuel pump replacement

Typical range: £180–£700+ depending on vehicle and tank access.

Fusebox or relay box repair

Typical range: £100–£500+.

Recovery if no-start

Typical range: £80–£250+ depending on distance and provider.

Repair Costs Guide UK OBD Fault Codes Hub
Diagnosis

How to diagnose P0629

A proper diagnosis should check whether the pump circuit is being held high because of a relay, wiring short, module issue or ECU command problem.

✅ Scan all modules and record related fuel, lean, misfire and no-start codes.

✅ Check if P0627 or P0628 are also stored.

✅ Check whether P0629 returns immediately after clearing.

✅ Check fuel pump relay operation and whether it is stuck closed.

✅ Check fuel pump fuse and relay box for heat damage.

✅ Check ECU command to the relay or fuel pump control module.

✅ Check voltage at the pump during key-on, cranking and engine running.

✅ Check whether voltage remains when the pump should be off.

✅ Inspect pump connector for corrosion, loose pins or water ingress.

✅ Inspect wiring near the tank, underbody and fusebox areas.

✅ Check fuel pressure under idle and load where possible.

✅ Check related codes such as P0171 and P0300.

✅ Confirm pump, module or ECU failure only after wiring and command checks pass.

Real experience

What I would check first

On a real P0629 fault, I would first check whether the fuel pump relay is stuck or whether the circuit has voltage when it should not. That helps separate a high circuit fault from a normal low-pressure fault.

Then I would check the pump module and wiring. If the control wire is shorted to power, the ECU may see high voltage even though the pump itself is not the root cause.

If the relay, wiring, command and voltage behaviour are correct but fuel pressure is wrong, then the pump or fuel pump control module becomes more likely.

Car Won’t Start Diagnosis Cranks But Won’t Start Diagnostic App
Vehicles commonly affected

Which vehicles commonly report P0629?

P0629 is a generic OBD-II code and can appear on many petrol and diesel vehicles with ECU-controlled fuel pump relays, fuel pump control modules or monitored fuel pump circuits.

Ford

Can appear on models using monitored fuel pump relay or fuel pump driver module circuits.

BMW

May appear on models with electric fuel pump modules and ECU-monitored fuel delivery circuits.

Volkswagen Group

Can appear on Volkswagen, Audi, Škoda and SEAT vehicles with electric fuel pump control faults.

Audi

May be logged where fuel pump relay, control module or wiring faults affect fuel delivery.

Mercedes-Benz

Can appear on vehicles using ECU-controlled fuel pump modules or relay-controlled fuel supply.

Other manufacturers

P0629 can also appear on Vauxhall, Peugeot, Citroën, Nissan, Toyota, Hyundai, Kia and other OBD-II vehicles.

Common mistakes

Mistakes to avoid with P0629

P0629 can be misdiagnosed if the fuel pump is replaced before the relay, module and wiring are tested.

Replacing the pump too quickly

A stuck relay, module fault or wiring short can trigger P0629 even with a good pump.

Ignoring voltage when pump should be off

A high circuit fault may show voltage at the wrong time.

Ignoring the relay box

Heat damage, corrosion or internal cross-feed can cause wrong pump circuit voltage.

Only checking fuel pressure

Fuel pressure matters, but P0629 also needs electrical command testing.

Ignoring wiring damage

Shorts to power, poor repairs or trapped wiring can create a high circuit signal.

Clearing the code before testing

Freeze-frame and related codes can show when the high circuit fault occurred.

MOT impact

Will P0629 fail an MOT?

P0629 itself is not usually the direct MOT failure item. The MOT concern is what it causes. If the vehicle will not start, cuts out, has an engine management light, fuel leak, poor running or unsafe behaviour, it can affect the MOT.

If the car has fuel pump control problems, poor running or cutting out symptoms, repair the fault before the MOT. A vehicle that stalls or refuses to start may not be suitable for testing.

⚠️ Higher risk: no-start, cutting out, fuel smell, engine light, poor running or unsafe fuel system fault.

⚠️ Medium risk: intermittent hard starting, stored P0629, hesitation or related lean/misfire code.

✅ Lower risk: fault repaired, normal fuel pressure, no warning lights and no drivability symptoms.

Engine Light MOT Guide Common MOT Failures
Fuel delivery reliability

Why fuel pump high circuit faults matter

Fuel pump control faults can stop the engine, affect fuel pressure or create unsafe running conditions. This matters for reliability, MOT preparation and everyday driving.

If the fault is active, diagnose it before long journeys, MOT testing or selling the vehicle.

Car Won’t Start Diagnosis Fault Codes Hub
Used car buying advice

P0629 on a car you want to buy

If a used car has P0629 stored, be cautious. It may be a wiring or relay issue, but it may also mean the fuel pump control module, relay box or pump circuit has a deeper fault.

Before buying, check whether the car starts cleanly from cold and hot, whether it cuts out, whether it loses power under acceleration and whether related lean or misfire codes are stored.

✅ Ask for a full diagnostic report, not just a cleared code.

✅ Check for P0627, P0628, P0171, P0300 or no-start related codes.

✅ Start the car several times during viewing.

✅ Road test under load if safe and legal.

✅ Be cautious if the seller says it only needs a relay without proof.

✅ Budget carefully if fuel pump module or wiring diagnosis is needed.

Used Car Buying Guides Inspection Checklist
Negotiation warning

Do not ignore pump control faults

A car may start fine during viewing but fail later if the pump relay, module or wiring fault is intermittent. That makes P0629 an important fault to price properly.

If the vehicle has already cut out, hesitated badly or failed to start, do not treat this as a minor stored code.

Buying With Advisories Check MOT History
Frequently asked questions

FAQs about P0629

Common questions about P0629 fuel pump A control circuit high faults, safe driving, no-start symptoms, repair costs and MOT impact.

What does code P0629 mean?

P0629 means the ECU has detected a high signal in the fuel pump A control circuit.

Is P0629 serious?

Yes. It can cause fuel pump control problems, no-start, hesitation, cutting out or poor acceleration.

Can I drive with P0629?

Only if the car starts and runs normally with correct fuel pressure. Cutting out or no-start means do not drive.

Does P0629 mean the fuel pump is faulty?

Not always. A stuck relay, wiring short, connector fault or control module can also cause this code.

Can a relay cause P0629?

Yes. A stuck fuel pump relay can keep the circuit live and trigger a high circuit fault.

Can bad wiring cause P0629?

Yes. A short to power, corrosion, trapped wiring or poor previous repair can trigger this fault.

Will P0629 fail an MOT?

It can affect an MOT if the vehicle will not start, cuts out, runs badly or has an engine warning light.

Can I clear P0629 without fixing it?

You can clear it, but if the high circuit fault remains, the code will return and symptoms may continue.

How much does P0629 cost to fix in the UK?

Diagnosis may cost £60–£150. Relay or wiring repairs may be cheaper, while pump/module repair can cost more.

What should I check first?

Check the fuel pump relay, fuse, pump command, voltage at the pump, ground, wiring shorts and fuel pressure.

About this guide

Written for practical UK fault finding

Motor Vehicle Expert explains diagnostic trouble codes in clear, mechanic-style language for UK drivers. This P0629 guide is designed to help you understand fuel pump A control circuit high faults, likely causes, safe driving advice, repair costs, MOT risks and used-car buying concerns before replacing expensive parts.

Fault codes should always be treated as a diagnostic starting point. P0629 can involve the fuel pump, relay, fuse, pump wiring, pump connector, fuel pump control module, ECU command, relay box, system voltage and fuel pressure. Proper testing is better than guessing.

For the full fault-code library, always start with the indexed OBD Fault Codes Explained UK hub.