Motor Vehicle Expert
OBD fuel pump low control circuit guide

P0628 Code Meaning UK

P0628 means “Fuel Pump A Control Circuit Low”. In plain English, the ECU or PCM has detected a lower-than-expected voltage signal in the fuel pump control circuit. This can cause low fuel pressure, hard starting, hesitation, poor acceleration, engine cutting out, limp mode or a car that cranks but will not start.

📅 Updated June 2026 🇬🇧 UK diagnostic guide 🛠 Fuel pump low circuit advice
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✓ Fuel pump low circuit explained ✓ Can you drive advice ✓ UK repair cost guide ✓ Live internal links only
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 P0628 mean?

P0628 means the fuel pump A control circuit is reading low. The ECU expects a certain voltage or response from the fuel pump control circuit, but the signal is lower than it should be.

This can happen if the fuel pump relay is weak, the fuel pump control module is faulty, the wiring has high resistance, the pump connector is corroded, the pump earth is poor, the fuse or power feed is weak, or the fuel pump itself is drawing the circuit down.

P0628 is important because fuel pump control affects fuel pressure. If the pump cannot receive proper voltage or command, the engine may crank but not start, cut out, hesitate or lose power when accelerating.

Most important first check

Check fuel pump fuse, relay, pump command, voltage at the pump, ground, connector condition and fuel pressure.

Main risk

Low pump circuit voltage can cause weak fuel pressure, stalling, poor acceleration 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

P0628 — Fuel Pump A Control Circuit Low

The fuel pump control circuit allows the ECU, fuel pump relay or fuel pump control module to supply and regulate the fuel pump. On many modern vehicles, the ECU monitors this circuit so it can detect open, low or high electrical faults.

When P0628 appears, the ECU is seeing a low signal. This may mean the circuit is shorted to ground, the voltage supply is weak, the wiring has high resistance, the pump control module is failing, the relay is not delivering enough voltage or the pump is pulling the circuit down.

P0628 is closely related to P0627 fuel pump A control circuit open, but P0628 points more towards a low-voltage or low-signal condition rather than a fully open circuit.

Mechanic view

Why P0628 needs voltage and pressure testing

I would not replace the fuel pump just because P0628 is stored. First, I would check whether the pump is being commanded, whether voltage reaches it properly and whether the pump ground is clean.

A pump can be blamed unfairly when the real issue is a weak relay, corroded connector, bad earth or high-resistance wiring. The opposite is also true: a failing pump can draw too much current and pull the circuit voltage low.

This is why P0628 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 P0628 code

P0628 symptoms usually come from poor fuel pump power, unstable fuel pressure or weak fuel delivery.

Hard starting

The engine may take longer to start if the pump builds pressure slowly.

Cranks but won’t start

If fuel pressure is too low, the engine may crank but not fire.

Engine cuts out

The vehicle may stall if the pump circuit voltage drops while driving.

Poor acceleration

Weak fuel pressure can cause hesitation, flat spots or poor throttle response.

Losing power under load

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

Engine management light

The engine warning light may appear with P0628 and related lean or misfire codes.

Lean running symptoms

Low fuel pressure may trigger lean running, rough idle or hesitation.

Intermittent no-start

A poor connector, relay or earth may make the fault come and go.

No fuel pump prime

In some cases, the pump may not prime properly when the ignition is switched on.

Common causes

What causes P0628?

P0628 is usually caused by low voltage, high resistance, poor ground or a failing component in the fuel pump control circuit.

Relay

Weak fuel pump relay

A relay may switch but still fail to deliver clean voltage to the pump circuit.

Fuse

Fuse or power feed issue

A poor fuse contact or weak power feed can drop voltage in the pump circuit.

Pump

Failing fuel pump

A worn pump can draw too much current, run slowly or pull circuit voltage down.

Wiring

High-resistance wiring

Damaged wires, rubbed looms or poor repairs can reduce voltage reaching the pump.

Connector

Corroded pump connector

Water ingress, loose pins or corrosion near the fuel tank can cause low voltage.

Ground

Bad fuel pump earth

A poor ground can make the pump circuit read low and reduce pump performance.

Module

Fuel pump control module fault

Some vehicles use a control module to regulate pump speed and pressure.

ECU

ECU command issue

Less commonly, the ECU may not command the pump circuit correctly.

Voltage

Low system voltage

A weak battery or charging fault can reduce voltage available to the fuel pump circuit.

Severity

How serious is P0628?

Low

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

Medium

Hard starting, hesitation, low fuel pressure warning signs or related lean/misfire codes.

High

No-start, cutting out, no pump prime, very low fuel pressure or stalling while driving.

Can you drive?

Can you drive with P0628?

You should only drive with P0628 if the car starts normally, runs smoothly and fuel pressure is confirmed correct. In that case, 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 very low fuel pressure. A low fuel pump control circuit 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 P0628, occasional hesitation or related lean codes.

🚫 Recovery may be needed: no-start, no pump prime, stalling, low fuel pressure or cutting out while driving.

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

Low fuel pump voltage can stop the engine

Fuel pumps need proper voltage and ground to work correctly. If the pump receives weak voltage, it may run but not deliver enough pressure.

If P0628 appears with P0171, P0300 or no-start symptoms, fuel pressure and pump voltage should be tested before long journeys.

P0171 Lean Fault P0300 Misfire Diagnostic App
Typical UK repair costs

How much does P0628 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 earth repair

Typical range: £60–£220+.

Fuel pump replacement

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

Fuel pump control module

Typical range: £150–£600+.

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 P0628

A proper diagnosis should check fuel pump command, circuit voltage, ground quality and fuel pressure. A low circuit code is often a voltage-drop problem, not just a dead pump.

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

✅ Check if P0627 or other fuel pump circuit codes are also stored.

✅ Listen for fuel pump prime where applicable.

✅ Check fuel pump fuse and relay operation.

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

✅ Check voltage at the fuel pump during prime and cranking.

✅ Check voltage drop on the power side of the pump circuit.

✅ Check fuel pump ground and voltage drop on the earth side.

✅ 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 failure only after power, ground and pressure checks pass.

Real experience

What I would check first

On a real P0628 fault, I would first check voltage at the pump while it is being commanded. A pump needs proper voltage under load, not just a quick reading with no current draw.

Then I would check the ground side. A weak earth can make the circuit read low and make the pump run slowly. This is easy to miss if you only check for battery voltage.

If voltage, ground and command are good but fuel pressure is low, then the pump itself becomes more likely.

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

Which vehicles commonly report P0628?

P0628 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

P0628 can also appear on Vauxhall, Peugeot, Citroën, Nissan, Toyota, Hyundai, Kia and other OBD-II vehicles.

Common mistakes

Mistakes to avoid with P0628

P0628 can be misdiagnosed if the fuel pump is replaced before voltage-drop and pressure testing.

Replacing the pump too quickly

A weak relay, bad ground or high-resistance wire can make a good pump run badly.

Only checking for voltage

Voltage must be checked under load because weak wiring may only fail when current flows.

Ignoring the ground side

A poor earth can create low circuit voltage and weak pump performance.

Ignoring fuel pressure

Electrical tests should be matched with fuel pressure readings.

Ignoring corrosion

Pump connectors near the tank can suffer water ingress and corrosion.

Clearing the code before testing

Freeze-frame and related codes help show when the circuit voltage dropped.

MOT impact

Will P0628 fail an MOT?

P0628 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 pressure 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 P0628, hesitation or related lean 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 low circuit faults matter

A low fuel pump control circuit can reduce fuel pressure and make the engine unreliable. That matters for safety, 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

P0628 on a car you want to buy

If a used car has P0628 stored, be cautious. It may be a wiring or relay issue, but it may also mean the fuel pump is failing or the fuel pump control module is weak.

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, 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 or wiring diagnosis is needed.

Used Car Buying Guides Inspection Checklist
Negotiation warning

Do not ignore fuel pressure symptoms

A car may start fine during viewing but fail later under load if the pump circuit voltage drops. That makes P0628 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 P0628

Common questions about P0628 fuel pump A control circuit low faults, safe driving, no-start symptoms, repair costs and MOT impact.

What does code P0628 mean?

P0628 means the ECU has detected a low signal in the fuel pump A control circuit.

Is P0628 serious?

Yes. It can cause low fuel pressure, no-start, hesitation, cutting out or poor acceleration.

Can I drive with P0628?

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

Does P0628 mean the fuel pump is faulty?

Not always. The relay, fuse, wiring, connector, ground or control module can also cause this code.

Can a weak relay cause P0628?

Yes. A weak fuel pump relay can reduce voltage to the circuit and trigger a low signal fault.

Can bad wiring cause P0628?

Yes. High-resistance wiring, corrosion or loose connector pins are common things to check.

Will P0628 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 P0628 without fixing it?

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

How much does P0628 cost to fix in the UK?

Diagnosis may cost £60–£150. Relay or wiring repairs may be cheaper, while fuel pump replacement can cost £180–£700+.

What should I check first?

Check the fuel pump fuse, relay, pump command, voltage at the pump, ground 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 P0628 guide is designed to help you understand fuel pump A control circuit low 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. P0628 can involve the fuel pump, relay, fuse, pump wiring, pump connector, fuel pump control module, ECU command, earth points, 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.