Treat P0628 as a reliability risk — the car may not restart or could stall unexpectedly, so diagnose it promptly and avoid long trips until the pump circuit is confirmed sound. P0628 means the engine computer sees low voltage on the control circuit it uses to command fuel pump 'A' — the wire or driver that switches the pump is reading lower than expected. It often shows up alongside no-start, hard-start or stalling complaints because the pump may not be running at the correct pressure.
What P0628 means
Rather than a simple on/off relay, many vehicles run the fuel pump through a control circuit — a fuel-pump driver/control module or a PWM output from the ECM that regulates how hard the pump works. The computer monitors that control line and expects a certain voltage. P0628 sets when it detects the circuit pulled low (a short to ground, an open with low reference, or a driver that cannot hold the commanded level). Because this is the command side of the pump rather than the pump's own speed feedback, the fault can either stop the pump entirely or leave it running at the wrong output, which is why symptoms range from a dead no-start to intermittent stalling. The cause is usually wiring, a connector or the pump-control module, though the pump and ECM output are also candidates.
Symptoms
- Engine cranks but will not start, or starts hard and stalls
- Loss of power, surging or stalling under load when pump output is wrong
- Low or unstable fuel pressure measured at the rail
- Fuel pump silent at key-on, or running at an incorrect speed
- Check-engine light with related low-fuel-pressure or lean codes
- Intermittent no-starts that come and go with connector movement or temperature
Common causes
- Corroded, loose or water-damaged connector at the pump, driver module or ECM
- Short to ground or chafed wiring in the pump-control circuit
- Failed fuel-pump driver/control module
- Worn or failing fuel pump drawing abnormal current
- Blown fuse or failed relay feeding the pump control circuit
- Faulty ECM control driver (least common, verify wiring first)
Severity & driving advice
Severity: High — A fuel-pump control fault can leave you stranded with a no-start or cause stalling in traffic.
Can I drive? Treat P0628 as a reliability risk — the car may not restart or could stall unexpectedly, so diagnose it promptly and avoid long trips until the pump circuit is confirmed sound.
Diagnostic approach
- Confirm the complaint and pressure — Check whether the pump runs at key-on and measure actual fuel-rail/pump pressure so you know if the pump is dead, weak or fine.
- Inspect power, ground and fuses — Verify the fuse, relay and pump grounds are good, since a lost feed or ground can pull the control line low.
- Back-probe the control circuit — With a meter, check the control-circuit voltage against the wiring diagram at the pump, the driver module and the ECM to locate where the reading goes low.
- Wiggle-test the harness and connectors — Flex the harness and reseat connectors while watching for the reading or symptom to change, catching intermittent opens and corrosion.
- Isolate module vs. pump vs. ECM — Once the circuit is verified, decide between the pump, the driver/control module and the ECM output — confirm the driver is receiving a good command before replacing the ECM.
Estimated repair costs
Typical US repair costs (parts & labour) for the faults behind P0628. These are national-average estimates, not a quote— your actual price varies by region, shop labour rate, and your vehicle’s make, model and year. Figures reviewed 2026.
| Repair | Estimated cost (USD) |
|---|---|
| Diagnosis (circuit + pressure test) | $90–$180 |
| Wiring / connector repair | $90–$350 |
| Fuel-pump driver / control module | $150–$500 |
| Fuel pump assembly replacement | $350–$900 |
FAQ
Does P0628 mean I need a new fuel pump?
Not necessarily. P0628 points to the pump's control circuit, so the cause is often wiring, a connector or the pump-control module — verify those before replacing the pump itself.
Why does my car sometimes start and sometimes not?
Intermittent no-starts usually mean a corroded connector or a chafed control wire that makes and breaks contact, which is why a wiggle-test of the harness is a key diagnostic step.
Can I drive with P0628?
It is risky — a control-circuit fault can cause a no-start or stalling, so it is best to get it diagnosed before relying on the car for longer drives.
What is 'fuel pump A'?
'A' simply designates the primary fuel pump (or its primary control circuit) on vehicles that may have more than one pump or control channel; it does not indicate a specific brand of part.