P0629 – Fuel Pump “A” Control Circuit High

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit High | Location: Designator A

Definition source: SAE J2012/J2012DA (industry standard)

DTC P0629 indicates the powertrain control system has detected a high electrical condition in the Fuel Pump “A” control circuit. “Circuit High” describes what the module sees on the control line (such as higher-than-expected signal/feedback or an inability to pull the circuit to the commanded state), not a confirmed failed fuel pump. The exact wiring layout and monitoring method vary by vehicle, so the same code can be set by different electrical faults depending on how the fuel pump is controlled (for example, via a relay, a dedicated driver module, or an integrated control stage). Always verify the specific circuit description, connector views, and test points in service information before testing.

What Does P0629 Mean?

P0629 means Fuel Pump “A” Control Circuit High. In practical terms, the engine control module (or another powertrain controller, depending on vehicle design) has determined that the electrical state of the fuel pump “A” control circuit is higher than expected when compared to what it is commanding or what it expects to observe. Under SAE J2012 DTC conventions, this is a circuit-level fault classification focused on the control circuit’s electrical behavior (such as a short-to-power, an open ground path, or an abnormal driver/feedback condition). The code by itself does not prove the pump is mechanically bad; it indicates the control circuit is not behaving as intended.

Quick Reference

• Subsystem: Fuel pump “A” control circuit (pump command/driver/relay control and related feedback, varies by vehicle).
• Common triggers: Control circuit pulled high when it should be low, short-to-power, open ground, incorrect backfeed through relay/module, or a driver/feedback mismatch.
• Likely root-cause buckets: Wiring/connector issues, power/ground faults, relay/control module faults (if used), fuel pump driver stage faults, controller output/driver problems.
• Severity: Often moderate to high; may cause no-start, stall, or reduced drivability depending on whether pump operation is affected.
• First checks: Scan for related codes, verify battery/charging health, inspect pump/relay/module connectors, check for harness damage near power sources, confirm command vs feedback in live data (if available).
• Common mistakes: Replacing the fuel pump first, skipping power/ground and backfeed checks, and ignoring connector pin fit/corrosion that can create a false “high” signal.

Theory of Operation

The fuel pump is typically controlled by a module output that switches a relay, commands a dedicated fuel pump control module, or directly drives the pump circuit. The controller expects the control circuit to change state in response to its command. Depending on design, the controller may monitor the control line directly, a driver feedback circuit, or a related confirmation signal that indicates the command has been carried out.

P0629 sets when the monitored circuit indicates a high input condition at a time the controller expects a different state. Common electrical reasons include a short-to-power on the control line, a missing ground path that prevents the circuit from being pulled low, backfeeding from another circuit, or an internal fault in a relay/module/driver that holds the line high. The exact monitor strategy and conditions for running vary by vehicle and should be confirmed in service information.

Symptoms

• No-start: Engine cranks but does not start if the pump is not being properly commanded or controlled.
• Stalling: Engine may stall unexpectedly if pump control is interrupted or the module disables operation.
• Extended crank: Longer-than-normal cranking before start due to inconsistent pump activation.
• Loss of power: Hesitation, weak acceleration, or reduced power if fuel delivery becomes unstable.
• Warning indicator: Malfunction indicator lamp illuminated; additional fuel or powertrain-related codes may be stored.
• Intermittent operation: Symptoms may come and go with vibration, temperature changes, or harness movement.

Common Causes

• Short-to-power in the fuel pump “A” control circuit wiring (chafed insulation contacting a power feed)
• Open or high-resistance ground on the fuel pump “A” control circuit (module command line pulled high due to missing ground reference)
• Corroded, water-intruded, loose, or damaged connectors at the fuel pump, fuel pump driver/relay area, or control module (causing unintended high signal)
• Incorrect relay installed, relay with internal short, or relay socket issues that backfeed voltage into the control circuit (varies by vehicle)
• Fuel pump driver module fault (if equipped) creating a biased/high output on the control line or feedback circuit (design varies by vehicle)
• Damaged harness routing near heat sources or moving components leading to intermittent short-to-power (often shows up during vibration/wiggle)
• Control module output driver fault that holds the fuel pump “A” control circuit high (verify wiring first)
• Aftermarket/added electrical equipment or wiring repairs that introduce backfeed or unintended power into the circuit

Diagnosis Steps

Tools typically needed: a scan tool capable of reading freeze-frame and live data, a digital multimeter, and a wiring diagram/service information for your exact vehicle. A back-probe kit, test light approved for automotive circuits, and basic hand tools help with connector checks. For intermittent faults, use live-data logging and, if available, a breakout lead to measure without damaging terminals.

1. Confirm the code and capture data: Verify P0629 is present. Record freeze-frame data and any related codes (especially fuel pump control, power supply, or module communication codes). Clear codes and see if P0629 resets immediately or only during a specific condition.
2. Check for symptoms and safety risks: Determine whether there is a no-start, stall, or reduced power condition. If the engine stalls or the vehicle won’t start, prioritize electrical checks before repeated crank attempts to avoid overheating wiring or components.
3. Review service information and circuit layout: Using the wiring diagram, identify what “Fuel Pump A” control circuit refers to on this platform (direct module output, relay control, or fuel pump driver module). Note connector locations, grounds, splices, and any feedback/monitor lines associated with the circuit (varies by vehicle).
4. Perform a focused visual inspection: Inspect the harness and connectors along the fuel pump control path: near the control module, relay/fuse area, underbody routing, and at the pump/driver module. Look for chafing, melted insulation, pin push-out, poor previous repairs, corrosion, and evidence of water intrusion.
5. Wiggle test with live-data logging: With the scan tool viewing relevant fuel pump command/status PIDs (names vary), gently wiggle the harness at key points and tap suspected connectors. Log data and watch for sudden changes or code reset. If the fault appears only during movement, suspect intermittent short-to-power or connector/terminal issues.
6. Check power supply integrity first: Verify the fuses and power feeds that supply the fuel pump circuit, relay, and any driver module are correct and secure. A misrouted feed or backfeed can make a control line read high. Confirm fuse fitment and inspect the fuse/relay box for heat damage or spread terminals.
7. Isolate the control circuit from the load: Key off, then disconnect the fuel pump connector and any intermediate driver/relay control connector as applicable. This helps determine whether the “high” condition is being induced by the pump/driver side or originates in the vehicle harness/module side.
8. Test for unwanted voltage on the control line: With the circuit disconnected (as appropriate for your design), measure whether the fuel pump “A” control circuit shows voltage when it should not. If voltage is present with the command inactive, suspect a short-to-power, relay backfeed, or incorrect wiring. Use service information to determine when the command is expected to be active.
9. Continuity and short-to-power checks: With power removed as required, check continuity of the control circuit end-to-end and test for short-to-power by measuring between the control wire and known power feeds. If a short-to-power is found, trace the harness for contact points, damaged insulation, or pinched sections.
10. Voltage-drop test critical grounds: Reconnect as needed and perform voltage-drop testing on the grounds used by the fuel pump, relay/driver module, and control module circuits during an active command (when safe to do so). Excessive drop indicates resistance in grounds or connectors that can skew circuit reference and contribute to a “high” reading.
11. Evaluate relay/driver behavior (if equipped): If the design uses a relay or fuel pump driver module, test for backfeeding at the relay socket/module connector. Swap with a known-good relay only if service information confirms the relay is identical and correct. If disconnecting the relay/driver removes the high condition, focus diagnosis there and on adjacent wiring.
12. Confirm repair with a road test and re-scan: After correcting the verified fault, clear codes and run the monitor by duplicating the conditions from freeze-frame data. Recheck for pending codes and review live data to confirm the control circuit responds normally without returning to a “high” state.

Professional tip: When chasing a “circuit high” fault, treat any sign of backfeed as a primary clue. Disconnecting components in the right order (load side first, then relay/driver, then module side) can quickly show whether the harness is being powered unintentionally or whether a module/driver output is stuck high. Always confirm terminal tension and pin fit; a loose terminal can mimic multiple electrical failures.

Possible Fixes & Repair Costs

Repair costs for P0629 vary widely because the fault can be caused by anything from a simple connector issue to a control module or pump circuit problem. Total cost depends on accurate diagnosis, parts quality/availability, labor time, and whether wiring repairs are needed.

• Repair wiring faults such as chafed insulation, short-to-power conditions, or damaged harness sections in the fuel pump “A” control circuit.
• Clean/secure connectors by addressing corrosion, moisture intrusion, bent pins, loose terminals, or poor pin fit at the pump, relay/module, and control module connections.
• Restore power and ground integrity by repairing/cleaning ground points, correcting incorrect power feeds, and fixing high-resistance connections found during voltage-drop testing.
• Replace a failed relay or fuse element if testing confirms the relay is stuck, incorrectly energized, or the circuit protection has been compromised (replace only after verifying the root cause of the circuit high condition).
• Replace the fuel pump control module (if equipped) when commanded outputs, feedback, and circuit checks confirm the module is driving or reporting an abnormally high control-circuit condition.
• Replace the fuel pump assembly only if circuit testing indicates an internal short-to-power or electrical fault related to the pump-side control circuitry (varies by vehicle design).
• Reprogram or replace the engine control module only after confirming all external circuits/components test good and the module output/monitoring is proven faulty per service information.

Can I Still Drive With P0629?

Driving with P0629 is not recommended unless the vehicle is operating normally and you can confirm there is no stalling, no-start condition, fuel smell, warning messages related to reduced power, or other safety concerns. Because this is a fuel pump “A” control circuit high fault, it can lead to unpredictable fuel delivery and sudden engine shutoff. If the engine stalls, struggles to start, loses power, or any safety-related symptoms appear (including reduced assist for steering or braking due to engine shutdown), stop driving and have the circuit diagnosed promptly.

What Happens If You Ignore P0629?

Ignoring P0629 can lead to intermittent or worsening driveability issues, including hard starts, stalling, or a no-start condition if the control circuit fault escalates. Continued operation with an unresolved circuit high condition can also increase stress on wiring, connectors, and control components, potentially causing additional electrical damage and making the eventual repair more complex.

Related Pump Fuel Codes

Compare nearby pump fuel trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P2930 – Fuel Pump Secondary Circuit High
• P025D – Fuel Pump Control Module Control Circuit High
• P0193 – Fuel Rail Pressure Sensor Circuit High
• P2909 – Exhaust Aftertreatment Fuel Injector Circuit High
• P2061 – Reductant Injection Air Pump Control Circuit High
• P0699 – Sensor Reference Voltage “C” Circuit High

Key Takeaways

• P0629 is electrical: it indicates a fuel pump “A” control circuit high condition, not a confirmed mechanical fuel issue.
• Wiring and connectors come first: shorts to power, poor grounds, and terminal fit problems are common root causes.
• Test before replacing parts: relays, modules, and pumps should only be replaced after circuit checks confirm failure.
• Severity can be high: a fault in the fuel pump control circuit can cause stalling or a no-start, creating safety risk.
• Vehicle design varies: use service information to identify the exact control strategy (relay, module, or direct control) and correct test points.

Vehicles Commonly Affected by P0629

• Vehicles with an electronic fuel pump control module (variable-speed pump control rather than simple relay-only designs).
• Vehicles using a fuel pump relay commanded by a control module with monitored feedback on the control circuit.
• High-mileage vehicles where harness flexing, heat exposure, and connector wear increase circuit faults.
• Vehicles operated in wet or corrosive environments where connector corrosion and moisture intrusion are more likely.
• Vehicles with recent electrical repairs where misrouted wiring, poor splices, or incorrect pinning can create a circuit high condition.
• Vehicles with underbody or rear-body harness exposure where debris impact or abrasion can damage pump circuit wiring.
• Vehicles with aftermarket electrical accessories installed where unintended backfeed/short-to-power conditions can affect control circuits.
• Vehicles with prior fuel system service where connectors may be left loose, seals damaged, or terminals spread.

FAQ

Does P0629 mean the fuel pump is bad?

No. P0629 only indicates the fuel pump “A” control circuit is reading or being driven “high” electrically. A fuel pump can be fine while a short-to-power, connector issue, relay/control module fault, or ground problem causes the circuit high condition. Testing is required to identify the root cause.

What does “control circuit high” usually indicate?

“Circuit high” typically points to an abnormally high electrical condition in the monitored control circuit, such as a short-to-power, an open ground path, unintended backfeed voltage, or a driver/output that is stuck high. The exact interpretation depends on how the vehicle monitors the fuel pump “A” control circuit.

Can a blown fuse cause P0629?

A blown fuse more commonly relates to a loss of power rather than a “high” condition, but circuit protection issues can be part of the overall fault path. For example, an incorrect fuse, a bypass, or damage from a short event can contribute to abnormal circuit behavior. Always diagnose the underlying cause before replacing fuses or relays.

Will clearing the code fix P0629?

Clearing the code only resets the stored fault information; it does not repair the electrical condition causing the circuit to be high. If the underlying issue is still present, the monitor will typically fail again and the code will return, sometimes immediately depending on the control strategy.

What should I check first for P0629?

Start with the basics: verify battery voltage stability, inspect the fuel pump “A” control circuit wiring and connectors for damage or corrosion, confirm grounds are clean and tight, and check for signs of short-to-power or backfeed. Then use service information to identify the correct control module/relay path and test the circuit with the proper procedure.

For the most accurate repair plan, confirm the vehicle’s specific fuel pump control design and connector pinouts using service information, then base each repair on measured evidence of a circuit high condition rather than replacing parts by guesswork.