Error code

OBD2 P0629

OBD2P0629
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Fuel Pump 'A' Control Circuit High.

Severity

moderateCan drive, but with reduced performance and potential for engine stalling.

Summary

P0629 indicates a high voltage condition in the fuel pump 'A' control circuit. This issue can affect both gasoline and diesel vehicles but is more common on modern returnless systems.

Symptoms

  • Engine stalls or shuts off unexpectedly
  • Rough, erratic idling or inability to idle
  • Reduced engine power throughout operating range
  • Stumbling or hesitation upon acceleration

Common Causes

  • Damaged wiring or connectors in the fuel pump circuit
  • Defective fuel pump relay
  • High system voltages due to charging system issues
  • Poor ground connections
  • Faulty sensors or control modules on returnless systems

Diagnosis

  1. Record all fault codes and freeze frame data.
  2. Check if the fuel system is constant-pressure or returnless.
  3. Inspect wiring between the PCM and fuel pump relay.
  4. Test continuity of the fuel pump control circuit.
  5. Verify ground connections in relevant circuits.

Fixes

  • Replace damaged wiring, connectors, or faulty relay

FAQ

What causes P0629?

Common causes include high voltage in the fuel pump control circuit due to damaged wiring, a faulty relay, or issues with system grounding.

How do I diagnose P0629?

Start by checking for high voltage conditions and inspecting the fuel pump's electrical connections. Ensure proper ground connections and test continuity in the control circuit.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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