P1931 — Fuel Additive Pump Overvoltage

P1931 — Fuel Additive Pump Overvoltage. P1931 identifies excessive voltage in the fuel additive pump control circuit.

For Ford vehicles

fuel additive pump control circuit – supply voltage too high

vehicle

Is it safe to drive?

Prompt electrical diagnosis recommended P1931 identifies excessive voltage in the fuel additive pump control circuit. Driving may be possible if the pump is not needed immediately, but an actual system overvoltage can damage the pump, control module, or other electronics. Stop driving and investigate if a battery-voltage warning, burning smell, overheating connector, or unstable electrical system is present.

Typical symptoms

The check-engine light illuminates and P1931 is stored in the powertrain controller.
The fuel additive pump remains silent when the control system commands it to operate.
The vehicle displays an incorrect-additive, dosing, or fuel-quality message on models equipped with that warning.
No fuel additive is delivered even though the additive tank contains fluid.
Measured charging voltage may be unusually high, particularly with electrical loads operating.
The vehicle may otherwise drive normally when P1931 affects only the additive-dosing circuit.

Common causes

A faulty alternator voltage regulator or excessive charging-system output can raise the voltage monitored by the P1931 circuit.
An improperly connected battery charger or jump-start device can impose excessive voltage on the vehicle electrical system.
An open or damaged voltage-sensing wire can create a falsely high supply-voltage reading at the fuel additive pump control circuit.
Corrosion, contamination, or a high-resistance ground connection can distort the voltage seen by the control module.
A short to another power circuit, damaged connector, or incorrectly wired relay can feed excessive voltage into the additive-pump control circuit.
A defective fuel additive pump control relay or internal control-module driver can cause P1931 even when the charging system is operating normally.

How to diagnose with an OBD scanner

Read P1931 with an OBD scanner Connect an ELM327-based scanner or use AIScanAuto to check stored and pending codes. Review the P1931 freeze-frame information and, where supported, monitor battery voltage, charging voltage, and fuel-additive pump commands while comparing the readings with the vehicle specifications.
Verify charging-system voltage Measure battery voltage with the engine off and again while the engine is running. Compare both readings with the charging label or service specification. If the running voltage is excessive, correct the alternator, regulator, battery, or connected charging device before continuing with P1931 diagnosis.
Inspect the additive-pump power path Examine the fuel additive pump connector, relay, fuse, wiring, and ground terminals for damage, corrosion, heat exposure, or aftermarket additions. Check for pin fretting, trapped moisture, or conductors pinched against metal.
Test the monitored supply voltage Using the correct wiring diagram, measure voltage at the additive-pump control connector under the specified operating conditions. Determine whether an excessive reading remains when the pump load is disconnected; this helps separate a wiring or relay fault from a pump or control-module fault.
Repair and confirm P1931 clearance Repair the confirmed overvoltage, open sensing circuit, defective relay, poor ground, or damaged connector. Clear P1931 with the scanner, command an additive-pump test if supported, and verify actual additive delivery before returning the vehicle to service.

Approximate repair cost

Estimated independent-shop cost is roughly $150-$1,000 USD for diagnosis and repair, depending on whether the fault is corrected through charging-system work, wiring or connector repair, or replacement of the additive pump control component. These figures are estimates only, not verified quotes, and costs vary by region, labor time, and parts availability.

Common questions

Does P1931 mean the fuel additive pump itself is defective?

Not necessarily. P1931 specifically indicates excessive supply voltage at the fuel-additive pump control circuit, so charging-system, wiring, ground, relay, and control-driver faults should be tested before replacing the pump.

Can the vehicle be driven with P1931 stored?

Limited driving may be possible if the additive system is not needed and charging voltage is normal, but P1931 should be investigated promptly. Do not continue driving if the battery is overcharging or any wiring shows heat damage.

Why can a wiring problem trigger a high-voltage code?

An open sensing lead, poor ground, or short to another power circuit can make the controller interpret the additive-pump supply as excessively high even when the alternator output is normal.

What should be checked first when P1931 appears?

Start by scanning the code and freeze-frame data, then measure battery voltage with the engine off and running. Confirm that the charging system is within specification before testing the additive-pump connector and wiring.

P1931 — ---

When your check engine light illuminates and a scan tool reveals code P1931, the vehicle's onboard computer has identified a malfunction within one of its sensor or actuator control circuits. P1931 specifically indicates that a driver circuit responsible for commanding a component has failed its diagnostic checks. The powertrain control module (PCM) continuously evaluates the output signals it sends to various actuators and the feedback it receives from sensors throughout engine operation. When these signals deviate from factory-defined parameters across multiple consecutive drive cycles, the PCM recognizes the pattern as a genuine fault rather than a one-time electrical glitch and stores P1931 in its memory.

The reason technicians emphasize freeze frame data when investigating P1931 is straightforward: this recorded snapshot captures the exact operating conditions present when the failure occurred. Engine speed, load percentage, coolant temperature, vehicle speed, and fuel trim values are all preserved, allowing you to recreate the circumstances that triggered the code. This dramatically narrows the diagnostic window and helps distinguish between a component that failed under specific conditions versus one that has completely died. P1931 does not pinpoint a single component—it marks a circuit-level issue that requires systematic elimination of potential causes.

The presence of P1931 typically means one of three things: the PCM is failing to properly control an actuator, a sensor is not returning expected feedback, or the wiring connecting these components has compromised integrity. Electrical faults of this nature rarely resolve themselves, and the underlying issue tends to worsen over time as corroded connections degrade further or damaged wires short completely.

Common Symptoms of P1931

The Check Engine Light remains illuminated until the fault is cleared
The affected system may operate erratically, intermittently, or cease functioning entirely
Depending on which circuit is compromised, the vehicle could enter limp-home mode with reduced power
Some drivers notice elevated fuel consumption due to compromised engine management
Automatic transmission shifting may feel harsh or delayed if the affected circuit relates to transmission control
Certain comfort or auxiliary systems (climate control, traction control) may disable themselves as a precaution

What Causes P1931?

Understanding the root causes helps you prioritize your troubleshooting approach:

Faulty control module driver circuit — The PCM itself may have an internal output stage failure, though this ranks among the less common culprits
Damaged or corroded electrical connector — Moisture intrusion, road salt, and age commonly degrade connector pins, increasing resistance or breaking contact entirely
Blown fuse protecting the circuit — A transient overcurrent event may have opened the protective fuse, removing power from the affected component
Insufficient ground connection — Corroded or loose chassis grounds prevent proper current return, creating voltage drops that the PCM interprets as circuit failure
Failed sensor or actuator component — The physical device itself may have died, leaving the circuit open or shorted
Open or shorted wiring harness — Wire insulation chafing, rodent damage, or heat-related deterioration creates breaks or unintended circuit paths

How to Diagnose P1931

Follow these systematic steps to isolate the exact failure point without replacing parts unnecessarily:

Connect a quality OBD2 scan tool, confirm P1931 is currently stored, and record all freeze frame data before clearing anything—this information is lost once the code resets
Pull all other stored trouble codes and note any P19xx series codes appearing alongside P1931, as these often share common power supplies, grounds, or communication buses that point toward the actual root cause
Research whether your specific make, model, and model year has published technical service bulletins addressing P1931—manufacturers occasionally release software updates or known-fix documentation for recurring electrical faults
Perform a thorough visual inspection of the wiring harness and connectors associated with the suspected circuit, looking for damaged insulation, pushed pins, green corrosion buildup, or melted plastic from overheating connectors
Use a multimeter to verify reference voltage, ground integrity, and signal continuity at the component connector while referencing factory wiring diagrams for expected values
Conduct a wiggle test by monitoring live scanner data while gently manipulating the harness—if signal values fluctuate during movement, you've located an intermittent wire break

Repair Options and Costs

Repair costs vary significantly depending on which component is actually responsible for P1931. Parts and labor estimates below reflect typical independent shop rates in USD:

Wiring harness repair or connector replacement — $80 to $250; often the only repair needed if inspection reveals damaged terminals or broken strands within an accessible location
Sensor or actuator replacement — $150 to $500; the specific part price varies considerably depending on the component—mass airflow sensors, throttle position sensors, and various solenoid valves fall within this range
Control module repair or replacement — $300 to $1,000; module repair through specialized electronics shops typically costs less than full replacement with a new unit

Total Repair Cost Summary

Most P1931 repairs fall between $80 and $250 when the issue involves wiring or connectors—the most frequently encountered cause. Sensor or actuator replacement occupies the mid-range, while PCM-level repairs represent the worst-case scenario. An accurate diagnosis before purchasing any parts is the single most effective way to manage repair spending on this code. Many shops charge a standard diagnostic fee of $75 to $150 that gets credited toward final repair costs if you proceed with their recommended solution.

Can You Drive with P1931?

P1931 carries a short-term drivability rating, meaning your vehicle remains functional with this code present, though with potential limitations. Performance may feel noticeably reduced if the engine enters reduced-power mode, and certain auxiliary systems could be disabled. However, if the code is accompanied by stalling, failure to start, or warnings related to braking or steering systems, treat the situation as urgent and have the vehicle towed rather than risk driving it further. Schedule diagnostic evaluation within a few days of code discovery to prevent minor electrical issues from cascading into larger problems.