P1731 — Insufficient Engine Speed Decrease During Self Test

P1731 — Insufficient Engine Speed Decrease During Self Test. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, blown fuse feeding the circuit, faulty sensor or actuator of the affected circuit.

For Ford vehicles

first to second upshifting error

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1731 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 insufficient engine speed decrease during self test for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1731 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1731 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P1731 usually costs between $80 and $1,000. 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 P1731?

Drivers most often notice: increased fuel consumption in some cases, Check Engine Light on, the affected system operates intermittently or not at all, possible limp mode depending on the affected component.

What does OBD2 code P1731 mean?

How do I diagnose P1731 myself?

Start with a scan: confirm P1731, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the sensor and actuator circuits, and verify the suspect component against live data before buying parts.

How much does it cost to fix P1731?

Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250; Replace the faulty sensor or actuator — $150–$500. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will P1731 clear itself?

Sometimes P1731 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

When your check engine light comes on and a scan tool pulls code P1731, your vehicle's control module has identified a problem with how engine speed responds during a diagnostic self test. P1731 stands for "Insufficient Engine Speed Decrease During Self Test" — a technical way of saying the engine did not slow down as expected when the computer asked it to. This code lives in the powertrain family, which covers both engine and transmission-related faults.

Modern engines rely on precise communication between sensors, actuators, and the ECU. During normal operation and self diagnostics, the control module commands certain components to adjust engine speed, then monitors how quickly and accurately the rpm responds. When that response falls outside the factory-calibrated range, the ECU flags P1731. The module also saves a freeze frame — a snapshot of live data including engine load, rpm, coolant temperature, and vehicle speed at the exact moment the fault occurred. Reviewing that snapshot first gives you a head start on diagnosis.

P1731 does not point to one specific part. Instead, it tells you that somewhere in the sensor and actuator circuits responsible for controlling engine speed, something is preventing proper operation. The underlying cause could be a faulty component, a wiring problem, a bad connection, or even a failed control module. Each of these requires a different repair approach, which is why a systematic diagnosis matters.

Common Symptoms of P1731

The check engine light is the most obvious clue. Beyond that, drivers typically notice one or more of the following:

The affected system may run intermittently or stop working entirely depending on which circuit is involved
Fuel consumption often climbs compared to normal driving
Some vehicles enter limp mode, limiting power or disabling certain functions to protect the drivetrain
Acceleration feel may be flat or unresponsive
Idle quality can suffer, with roughness or fluctuation
In rare cases, the engine may stall or hesitate under load

What Causes P1731?

The root cause can live anywhere in the affected circuit. Here are the most frequent culprits, listed from most to least common:

A faulty sensor or actuator that no longer responds correctly to commands
Corroded, loose, or physically damaged electrical connectors that interrupt signals
An open circuit or short in the wiring harness
A poor ground connection at the component or control module
A blown fuse feeding power to the circuit
In rare cases, an internal failure inside the ECU or transmission control module itself

How to Diagnose P1731

Follow these steps in order to avoid replacing good parts:

Connect an OBD2 scanner and confirm P1731 is stored. Record the freeze frame data — it shows the engine conditions when the fault triggered and guides your testing.
Pull all stored and pending codes. P1731 often appears alongside other codes that identify the specific circuit or component at fault.
Check for any manufacturer TSBs related to P1731 or similar self-test failures for your make, model, and year. Factory bulletins sometimes reveal known issues or software updates that fix the problem without parts replacement.
Perform a thorough visual inspection of the wiring harness and connectors tied to the engine speed control circuit. Look for broken insulation, burned wires, corrosion buildup, and any connectors that are not fully seated.
Test reference voltage, ground integrity, and signal continuity at the component connector using a multimeter. Compare your readings to factory specifications.
Wiggle-test the harness while monitoring live data on the scanner. Any signal dropouts or erratic readings point to broken wires inside the insulation.
Clear the code, complete a full drive cycle covering the conditions captured in the freeze frame, then re-scan to confirm P1731 does not return.

Repair Options and Costs

Start with the least expensive possibilities before moving to costlier fixes:

Wiring harness repair or connector replacement: $80–$250
Faulty sensor or actuator replacement: $150–$500
Control module repair or replacement: $300–$1,000

Prices reflect parts and labor at independent shop rates in USD. Wiring repairs are often quick fixes that take an hour or less. Sensor or solenoid replacement varies by location and accessibility. Control module work requires the most labor and sometimes involves reprogramming, which pushes costs toward the high end.

Total cost for most P1731 repairs falls between $80 and $1,000 depending on what failed. A solid diagnosis before buying parts prevents overspending — the most expensive scenario is rarely the first thing to check.

Can You Drive with P1731?

Most vehicles stay drivable with P1731 stored. You may notice reduced performance, poor throttle response, or an auxiliary system that stops working. The car will not typically leave you stranded. However, if the car stalls, fails to start, or displays brake or steering warnings, stop driving immediately and have it towed. When in doubt, treat the code as a reason to schedule repair soon rather than ignore it.