P0629
UniversalFuel Pump A Control Circuit High. This indicates that the Powertrain Control Module (PCM) has detected an abnormally high voltage condition in the electrical circuit that controls the primary fuel pump.
High SeverityThe Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an abnormally high voltage reading in the control circuit for Fuel Pump A, often indicating an electrical short or a fault within the fuel pump control module itself. This condition typically results in the engine failing to start or stalling shortly after starting, as the fuel pump may not receive the correct signals to operate, leading to a lack of fuel delivery to the engine.
⚠️ Before You Begin (Safety First)
Warning: Always disconnect the battery before working on electrical components. Fuel systems are under pressure; exercise extreme caution when disconnecting fuel lines to prevent fuel spray and potential fire hazards. Allow the engine to cool before working around hot components.
Common Symptoms
- Engine will not start or cranks but does not fire
- Engine stalls shortly after starting
- Check Engine Light illuminated
- Reduced engine performance or hesitant acceleration
Common Causes
- Short to voltage in the fuel pump control circuit
- Faulty fuel pump driver module (FPDM)
- Defective fuel pump relay
- Corroded or damaged wiring in the fuel pump circuit
- Faulty Powertrain Control Module (PCM)
Frequently reported on: Ford F-150 (2004-2010), Chevrolet Silverado (2007-2013), Dodge Ram (2009-2012), General/Universal
Diagnostic Steps
- Check all related fuses for the fuel pump and its control module for continuity.
- Inspect the fuel pump relay for proper operation; try swapping it with a known good relay if available.
- Visually inspect the wiring harness leading to the fuel pump and its control module for any signs of damage, chafing, or corrosion.
- Using a multimeter, test for proper voltage at the fuel pump connector and the fuel pump driver module, consulting your vehicle's specific wiring diagram.
- If accessible and suspected, test or replace the fuel pump driver module.
👨🔧 When to Call a Professional
If initial checks of fuses and relays do not resolve the issue, or if you are uncomfortable with advanced electrical diagnostics involving multimeters and wiring diagrams, it is best to consult a certified automotive technician to prevent further damage.
Commonly Asked Questions
Can I drive my car with a P0629 code?
No, it is generally not advisable to drive with a P0629 code, as it indicates a critical issue with fuel delivery that can cause the engine to stall unexpectedly or prevent it from starting at all, creating unsafe driving conditions.
What's the difference between 'Fuel Pump A' and 'Fuel Pump B'?
In vehicles with multiple fuel pumps or complex fuel systems, 'Fuel Pump A' typically refers to the primary fuel pump or the main circuit controlling it, while 'B' would indicate a secondary or auxiliary pump/circuit.
Is the P0629 code always a faulty fuel pump?
Not necessarily. While it affects fuel delivery, the code specifically points to a problem within the fuel pump's control circuit, which could be a wiring issue, a relay, or a separate fuel pump driver module, rather than the pump itself.
How can I tell if the issue is a fuse or a relay?
Fuses can be visually checked for a broken wire or tested with a multimeter for continuity. Relays can sometimes be tested by listening for an audible click when activated or by temporarily swapping it with an identical, known-good relay from another circuit (e.g., horn relay).
What does 'circuit high' mean for a fuel pump control circuit?
'Circuit high' typically means the PCM is detecting a voltage in the circuit that is higher than the expected operating range. This could be due to a short to voltage (e.g., a wire touching a constant 12V source), or an internal fault within the control module causing it to output an incorrect voltage.