P0629Generic code

P0629 Code: Fuel Pump "A" Control Circuit High

The P0629 code means the computer sees high voltage in the fuel pump control circuit, from an open circuit or a short to voltage. It can make the engine crank without starting or stall. Check the connector and wiring first.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$30 to $900
Difficulty
Medium
System
Fuel Injection
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0629 code means

The computer turns on the fuel pump through a relay or a pump control module. When you turn the key on, it runs the pump for 2 or 3 seconds to pressurize the system, and it keeps the pump running while the engine turns.

The computer watches the control circuit from its own driver transistor. The P0629 code flags high voltage in that control circuit, either an open circuit or a short to voltage. Before you replace the component, check the fuse, relay, connector and wiring, which are the most common causes.

If the control circuit fails, the pump may not run at all (the engine cranks but does not start) or it may run all the time (and drain the battery). On many vehicles the pump module sits under the rear seat or in the trunk, and it corrodes with moisture.

To confirm the fault, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be under 1 ohm, and an infinite reading means the wire is open. If the wiring is good, measure the component itself: infinite resistance confirms it is open inside.

P0629 code symptoms

  • Check engine light on.
  • The engine cranks but does not start.
  • The engine stalls while driving or at a stop.
  • No humming from the fuel pump when you turn the key on.

Likely causes of the P0629 code

  1. Loose or broken connector. The most frequent cause, especially after another repair.
  2. Open coil or motor. Infinite resistance.
  3. Control wire cut between the component and the computer.
  4. Short to 12 volts. The control wire touches another wire that carries voltage.

How to diagnose the P0629 code step by step

  1. Activate the component with the scan tool and check whether it responds.
  2. Check the fuse and relay. Measure the voltage on both sides of the fuse, and swap the relay with an identical one.
  3. Measure the supply at the connector. You should see battery voltage with the key on or when the component is activated.
  4. Measure the resistance of the component and compare it with the manual. Also check the insulation to ground.
  5. Check the control wire for continuity to the computer and for shorts.
  6. Listen to the pump when you turn the key on. It should run for 2 to 3 seconds.
  7. Measure the fuel pressure.

How to fix the P0629 code

  • Repair the connector, the wiring or the power supply.
  • Replace the fuel pump control if it does not respond even with correct power and command signals.
  • Clear the codes and verify the repair.

Technical reference data

  • Typical pump current draw: 4 to 8 amps.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

The pump control module is a known weak point on several makes, so it is worth testing it early.

P0629 on Ford

On Ford, the fuel pump control module is a known failure.

P0629 on GM

On GM, the fuel pump control module is a known failure.

P0629 on Chrysler

On Chrysler, the fuel pump control module is a known failure.

Frequently asked questions about P0629

Can I drive with a P0629 code?
Yes, with caution. If the pump stops working, the engine will stall or will not start, so do not rely on the vehicle for long trips until it is fixed.
What does the fuel pump control do?
The computer turns the pump on through a relay or a control module. It runs the pump for 2 or 3 seconds when you turn the key on, then keeps it running while the engine turns.
Do I always have to replace the part?
No. Check the fuses, relays, connectors and wiring first, because they are the most common cause.
How much does it cost to fix P0629?
As a rough guide, between $30 and $900. A connector or wiring repair is at the low end, and a new pump module is at the high end.
What does the P0629 code mean?
It is a generic OBD2 code that means the computer sees high voltage in the fuel pump control circuit, from an open circuit or a short to voltage.
What is the most common cause of P0629?
With a P0629 code, the usual culprit is a loose or broken connector, especially after another repair was done nearby. An open pump circuit or a cut control wire also set it.

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