Faulty sub-throttle position sensor (TPS) or its internal circuitry.; Wiring damage or poor connection at the sub-throttle position sensor connector.; Carbon buildup or mechanical binding on the sub-throttle plate, causing incorrect sensor readings.; Failed sub-throttle actuator motor, preventing proper plate movement.; Corrosion or damage to the ECM connector or internal ECM fault (rare).; Intake air leaks or unmetered air affecting throttle performance.; Aftermarket or improperly installed throttle body components causing misalignment.

DTC codes / Toyota codes / P1401

P1401 · ToyotaSub-Throttle Position Sensor Range Performance Problem

Q: What does code P1401 mean?

Sub-Throttle Position Sensor Range Performance Problem. P1401 is a Toyota-specific code indicating that the sub-throttle position sensor (a secondary throttle plate sensor used for traction control) is reporting a range or performance problem to the engine control module (ECM). The ECM has detected that the sensor's signal is out of expected limits during self-tests or does not correlate with other throttle inputs, often due to a faulty sensor, wiring issue, or carbon buildup.

P1401 is a Toyota-specific code indicating that the sub-throttle position sensor (a secondary throttle plate sensor used for traction control) is reporting a range or performance problem to the engine control module (ECM). The ECM has detected that the sensor's signal is out of expected limits during self-tests or does not correlate with other throttle inputs, often due to a faulty sensor, wiring issue, or carbon buildup.

SystemPowertrain

Code typeToyota specific

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Intermittent or permanent reduction in engine power, especially during acceleration or when traction control activates.
Rough idle or hesitation when the sub-throttle plate fails to respond correctly.
Traction control or vehicle stability control (VSC) warning light may also turn on.
In some cases, the engine may enter limp mode, limiting speed and RPM.

Common causes, most likely first

Faulty sub-throttle position sensor (TPS) or its internal circuitry.
Wiring damage or poor connection at the sub-throttle position sensor connector.
Carbon buildup or mechanical binding on the sub-throttle plate, causing incorrect sensor readings.
Failed sub-throttle actuator motor, preventing proper plate movement.
Corrosion or damage to the ECM connector or internal ECM fault (rare).
Intake air leaks or unmetered air affecting throttle performance.
Aftermarket or improperly installed throttle body components causing misalignment.

How to diagnose and fix it

Use an OBD-II scanner to retrieve the freeze frame data and verify the sub-throttle position sensor voltage readings.
Visually inspect the sub-throttle position sensor connector and wiring for corrosion, loose pins, or damage; repair as needed.
Clean the throttle body and sub-throttle plate with approved throttle body cleaner to remove carbon deposits.
Perform a resistance and voltage test on the sub-throttle position sensor according to Toyota service information; replace if out of specification.
Check the sub-throttle actuator motor operation and replace if binding or non-functional.
Reset the ECM and perform a throttle body calibration or relearn procedure as required for the specific Toyota model.
If all else fails, diagnose the ECM for internal faults, though this is rare and should be confirmed by a professional.

Common misdiagnosis traps for P1401

Many technicians replace the sub-throttle position sensor without first cleaning the throttle body, but carbon buildup often causes the sensor to read out of range and mimics a failed sensor.
The sub-throttle position sensor is often confused with the main throttle position sensor; they are separate components, and P1401 specifically refers to the sub-throttle circuit.
A weak battery or charging system issue can cause erratic sensor readings and set P1401, so always check battery voltage and ground connections before condemning parts.
On some Toyota models, the sub-throttle position sensor is integrated into the throttle body assembly, requiring replacement of the entire unit rather than just the sensor.
Intermittent wiring faults at the sensor connector can be temperature-sensitive, so wiggle-test the harness while monitoring live data to catch the glitch.

Can I keep driving with P1401?

You can usually drive the vehicle with P1401, but expect reduced engine power and possible activation of the traction control warning. Avoid heavy acceleration or towing until the fault is repaired, and if the engine enters limp mode, have the vehicle serviced promptly.

Tools that help

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Guidance is general and written for Toyota vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.