Powertrain, generic · Computer and auxiliary outputs

P0629 Fuel Pump A Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel pump relayfuel pump driver modulefuel pumpengine control module

Related codes

P0627P0628P062AP0232P025A

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com.