P0629: Fuel Pump A Control Circuit High

What 'fuel pump A control circuit' means differs by maker: at GM petrol engines it is the control line from the engine module to the fuel pump relay (high-side driver), at GM's LML diesel the lift pump, at Ford petrol engines with a pump driver module the secondary circuit from that module to the pump (reported as a duty cycle on a monitor line), and at Ford's 6.7 L diesel (F-650/750) the high or low side of the pump relay. P0629 means a short to battery voltage: GM detects voltage at the output while the driver is off (8 of 10 samples at 250 ms, two trips in 2018); because the driver hardware cannot always separate open circuit and short to voltage, P0627 may set as well. Ford's 6.7 L diesel reports a short to voltage on the high side of the pump relay within 0.2 s. If the pump can no longer be switched off it may keep running after switch-off and drain the battery.

Medium severity. Can I keep driving?Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

Symptoms

Pump runs constantly or after switch-off
Battery drained
Possibly no start
Check engine light on

Most likely causes

Control wire shorted to a battery feed
Relay contacts welded or relay faulty internally
Moisture in the relay or fuse box
Driver in the engine module shorted

What to check, in order

Start with the simplest. You can tick off each step.

Check the pump's fuse, relay, and connector
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Replace the filter if it is due for maintenance
Compare commanded and actual pressure in live data
Measure the pressure with a suitable gauge
Check the sensor and regulator before replacing the pump

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P0629 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
6: Control modules and outputs
29: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0629?

Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

What causes code P0629?

The most common causes are: control wire shorted to a battery feed; relay contacts welded or relay faulty internally; moisture in the relay or fuse box.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.