P0629 — Fuel Pump "A" Control Circuit High

OBD2 code P0629 flags a problem with the fuel delivery and mixture control (fuel pump "A" control circuit high). Short, gentle driving to a shop is usually possible. Common culprits: faulty fuel pressure regulator, vacuum or intake leaks skewing the mixture, clogged or leaking fuel injectors.

powertrain (engine/transmission)

Is it safe to drive?

Drive with caution Drive with caution. Mixture and fuel-pressure faults can cause stalling, hesitation in traffic and — when severe — catalyst damage. Avoid long trips until diagnosed.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0629 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the fuel delivery and mixture control for damage, corrosion, chafing or poor contact.
Subsystem check With the fuel pump "A" control disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
Subsystem check Measure fuel pressure at the rail and compare with factory specification at idle and under load.
Subsystem check Check short-term and long-term fuel trims in live data to see which way the mixture is off.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0629 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0629 (parts and labor, USD, independent shop rates): Replace the fuel pump: $400–$900; Replace the pressure regulator or sensor: $150–$450; Clean or replace injectors: $200–$800; Replace the fuel filter: $80–$200. Overall, fixing P0629 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P0629?

Drivers most often notice: increased fuel consumption, loss of power under load, Check Engine Light on, fuel smell in severe cases.

What is the most common cause of P0629?

The most common causes are: faulty fuel pressure regulator, vacuum or intake leaks skewing the mixture, clogged or leaking fuel injectors.

How do I diagnose P0629 myself?

Start with a scan: confirm P0629, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the fuel pump "A" control, and verify the suspect component against live data before buying parts.

How much does it cost to fix P0629?

Replace the fuel pump — $400–$900; Replace the pressure regulator or sensor — $150–$450; Clean or replace injectors — $200–$800; Replace the fuel filter — $80–$200. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P0629?

Drive with caution. Mixture and fuel-pressure faults can cause stalling, hesitation in traffic and — when severe — catalyst damage. Avoid long trips until diagnosed.

When your scanner pulls code P0629, it's telling you that the engine computer has detected an abnormal voltage condition on the fuel pump "A" control circuit. Specifically, the signal it's reading sits higher than it should — typically right at battery voltage or close to it. This places the fault squarely in the fuel delivery and mixture control portion of your emissions system, which falls under the powertrain category in the OBD2 standard.

The engine control module (ECM or PCM) constantly watches the voltage on this circuit while the engine runs. Under normal conditions, the signal toggles or sits at a predictable level based on fuel demand. When something pulls that line up to full battery voltage and holds it there, the module logs the abnormality. If it persists long enough across consecutive drive cycles, P0629 gets stored and the Check Engine light illuminates. The freeze frame data captured alongside the code is particularly useful — it records RPM, engine load, coolant temperature, and vehicle speed at the exact moment the fault first triggered.

There are essentially three scenarios that trigger this circuit-high condition. A short to a positive power source somewhere in the wiring will force the voltage up. An open ground return can cause the circuit to float high instead of pulling low properly. Or the fuel pump control itself has failed in a way that clamps the signal line to voltage. Each requires a different repair approach, which is why proper diagnosis matters before you start replacing parts.

Common Symptoms of P0629

The Check Engine light is on and stays on
Fuel economy has noticeably dropped
The engine feels sluggish or lacks power when you put load on it
Hard starting — the engine cranks longer than normal before catching
Rough idle or hesitation when accelerating
A fuel smell, especially if the problem is advanced
In severe cases, the engine may stall or stumble while driving

What Causes P0629?

Most often, the root cause is electrical rather than mechanical. Here are the typical culprits, ordered from most to least frequent:

The signal wire to the fuel pump control is shorted to battery positive somewhere in the harness
An open or disconnected ground return on the fuel pump "A" control circuit
The fuel pump control module or driver itself has failed and is pulling the signal high
A weak or failing fuel pump creating abnormal pressure readings
A clogged fuel filter restricting flow and causing secondary electrical stress
A faulty fuel pressure regulator throwing off system pressure
Vacuum leaks or intake manifold issues that upset the air-fuel mixture
Contaminated or improper fuel affecting injector behavior and sensor readings

How to Diagnose P0629

Follow these steps in order to avoid replacing good parts:

Plug in your OBD2 scanner, confirm P0629 is present, and record all freeze frame data. Note the RPM, load, temperature, and speed values — you'll use these to recreate the fault condition later.
Pull any related codes from the ECM. Codes that appear alongside P0629 often point to the actual failure. Check manufacturer TSBs (Technical Service Bulletins) for your specific make, model, and year — many common faults have published solutions or software updates.
Inspect the wiring harness and connectors associated with the fuel pump control circuit. Look for chafed insulation, broken wires, corrosion at the connector pins, or loose fittings. This step catches most wiring-related failures.
Disconnect the fuel pump connector and probe the signal wire at the harness side with a multimeter. If you still read battery voltage with the pump unplugged, the short exists in the wiring. If the voltage drops to normal operating range, the fuel pump control driver inside the module is likely failed.
With the engine running (or at idle per factory specs), check fuel pressure at the rail and compare to manufacturer specifications. Low or high pressure points toward a mechanical fuel system problem.
Monitor short-term and long-term fuel trims in your scanner's live data. Consistently positive or negative trims indicate whether the mixture is running rich or lean, which helps narrow the system at fault.
Clear the code, complete a drive cycle that reproduces the freeze frame conditions, and verify the light stays off. If P0629 returns, you have an active fault that needs repair.

Repair Options and Costs

Labor rates and parts prices vary by region and shop, but here are typical ranges in USD for independent repair shops:

Fuel pump replacement: $400–$900 (parts and labor)
Fuel pressure regulator or sensor replacement: $150–$450
Fuel injector cleaning or replacement: $200–$800
Fuel filter replacement: $80–$200

Begin with the least expensive and most likely fixes — wiring issues, connectors, and the fuel filter — before moving to major components like the fuel pump or injectors.

Total Repair Cost Summary

Depending on what actually failed, fixing P0629 typically runs between $80 and $900 including parts and labor. A fuel filter is the cheapest possible fix. Fuel pump replacement represents the high end. Getting an accurate diagnosis first prevents wasting money on parts you don't need — the most expensive scenario is almost never where you should start.

Can You Drive with P0629?

Drive with caution. This code affects fuel delivery and mixture control, both of which directly impact engine operation. Symptoms like stalling, hesitation, or power loss can occur without warning — dangerous in traffic or at speed. Extended operation with a severe fuel delivery fault can also allow unburned fuel to enter the exhaust and damage the catalytic converter. Avoid long trips until the problem is diagnosed and repaired.