Fuel Pump "A" Control Circuit /Open
P0627 indicates an open or disconnected circuit in the fuel pump control system. The engine control module cannot properly command the fuel pump to operate, preventing fuel delivery to the engine and making it unable to start or run.
What You Might Notice
- Check engine light illuminated
- Engine will not start or cranks but does not turn over
- Engine stalls or dies immediately after starting
- Engine misfires or runs rough when it does start
- Reduced fuel economy or difficulty reaching operating temperature
Most Common Causes
- 1
Fuel pump relay failure
The relay that controls power to the fuel pump has failed or is not switching properly, breaking the control circuit.
- 2
Wiring harness open or disconnected
The electrical wiring between the ECU and fuel pump is broken, corroded, or disconnected at connectors.
- 3
Fuel pump motor failure
The fuel pump itself has an internal open circuit or winding failure, preventing it from receiving control signals.
- 4
ECU fuel pump control module failure
The engine control unit has a faulty fuel pump control circuit or damaged output driver transistor.
How to Diagnose It
- 1
Check Fuel pump relay failure — The relay that controls power to the fuel pump has failed or is not switching properly, breaking the control circuit.
- 2
Check Wiring harness open or disconnected — The electrical wiring between the ECU and fuel pump is broken, corroded, or disconnected at connectors.
- 3
Check Fuel pump motor failure — The fuel pump itself has an internal open circuit or winding failure, preventing it from receiving control signals.
- 4
Check ECU fuel pump control module failure — The engine control unit has a faulty fuel pump control circuit or damaged output driver transistor.
How to Fix It
- 1
Test and replace fuel pump relay
Locate the fuel pump relay in the vehicle's relay box, test it with a multimeter for continuity, and replace if faulty. Verify power and ground signals at the relay terminals.
- 2
Inspect and repair fuel pump wiring
Check the fuel pump control circuit wiring for breaks, corrosion, or loose connectors between the ECU and fuel pump. Repair or replace damaged wire segments and clean corroded connector terminals.
- 3
Replace fuel pump assembly
If wiring and relay test good, the fuel pump motor likely has an internal failure. Remove and replace the fuel pump module in the fuel tank.
- 4
Test ECU and replace if needed
If all wiring, relay, and pump components test good, the ECU fuel pump driver output may be damaged. Have the ECU tested or replaced by a qualified technician.
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