Short to voltage or damaged wiring in the fuel pump control circuit; Faulty fuel pump relay or its socket and connections; Faulty fuel pump driver or control module (where fitted); Corroded or loose connector at the fuel pump, relay box or control module; Fuel pump fault drawing abnormal current or feeding back into the circuit; Fault inside the engine control unit.

P0629

Fuel Pump A Control Circuit High.

Generic
Powertrain
Generic code
High severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
29: FaultThe specific fault in that area

What it means

P0629 means the engine control unit has detected a high voltage condition in the control circuit for fuel pump A. The control unit monitors the circuit that drives the pump, relay or pump driver module, and sets the code when the signal is higher than expected for the commanded state. Exact circuit layout and the way the fault is detected vary by vehicle and engine.

Symptoms

Engine cranks but is hard to start or will not start
Engine stalls or cuts out while driving
Loss of power or hesitation under load
Fuel pump not heard priming when ignition is switched on
Engine warning light on, sometimes with other fuel pressure codes

Possible causes

Short to voltage or damaged wiring in the fuel pump control circuitlikely
Faulty fuel pump relay or its socket and connectionslikely
Faulty fuel pump driver or control module (where fitted)possible
Corroded or loose connector at the fuel pump, relay box or control modulepossible
Fuel pump fault drawing abnormal current or feeding back into the circuitpossible
Fault inside the engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, noting whether other fuel pressure, pump module or voltage codes are present
Check the battery condition and charging voltage, as abnormal supply voltage can upset circuit monitoring
Inspect the fuel pump relay, fuse and socket for heat damage, corrosion and bent or loose terminals
Inspect wiring and connectors between the control unit, relay or driver module and the fuel pump, looking for chafing, water ingress and pin damage
With the ignition on, listen for the pump priming and use a scan tool to command the pump on and off if the vehicle supports it
Using the wiring diagram for the specific model, measure voltage at the control circuit with the pump on and off and check for shorts to voltage
Test the relay or driver module and the pump's current draw against the manufacturer's specification
Check fuel pressure against the manufacturer's specification to confirm whether the pump is delivering properly

How to fix

Repair or replace damaged wiring and restore any shorts to voltage in the control circuit
Replace a faulty fuel pump relay and clean or repair its socket
Replace the fuel pump driver or control module if testing shows it is faulty, following any coding or adaptation steps the manufacturer requires
Clean or replace corroded or damaged connectors and terminals
Replace the fuel pump if it is found to be causing the fault
Replace or repair the engine control unit only after all wiring and component checks have been completed

Can I keep driving?

High severity

Avoid driving if you can. A fault in the fuel pump control can cause the engine to stall without warning, which is unsafe in traffic, so have it checked before further use.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.