P0628Generic code

P0628 Code: Fuel Pump "A" Control Circuit Low

The P0628 code means the computer sees low voltage in the fuel pump control circuit, from a short to ground or a lack of power. It can make the engine crank without starting or stall. Check the fuse, relay, 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 P0628 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 P0628 code flags low voltage in that control circuit, either a short to ground or a lack of power. 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, unplug the component with the key on and see what happens to the reading or the code. If the value jumps to the opposite extreme, the wiring is good and the component is the one pulling the signal to ground. If nothing changes, look for the short in the wire, starting where the harness rubs against the engine, the chassis or the exhaust.

P0628 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 P0628 code

  1. Control wire shorted to ground. The component may stay on all the time, or the computer cuts the command to protect itself.
  2. Interrupted power supply. A blown fuse, a faulty relay or a cut wire.
  3. Shorted component. Its resistance is much lower than specified.
  4. Connector with moisture. It creates a path to ground.

How to diagnose the P0628 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 P0628 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.

P0628 on Ford

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

P0628 on GM

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

P0628 on Chrysler

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

Frequently asked questions about P0628

Can I drive with a P0628 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 P0628?
As a rough guide, between $30 and $900. A fuse or connector repair is at the low end, and a new pump module is at the high end.
What does the P0628 code mean?
It is a generic OBD2 code that means the computer sees low voltage in the fuel pump control circuit, from a short to ground or a loss of power.
What is the most common cause of P0628?
With a P0628 code, the usual culprit is a control wire shorted to ground, a blown fuse or a faulty relay. Moisture in a connector can also create a path to ground.

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