Loose, corroded, or damaged electrical connector at the motor torque sensor; Chafed or broken wiring in the motor torque sensor circuit; Failing motor torque sensor; Faulty hybrid vehicle control module or inverter assembly; Electromagnetic interference from aftermarket accessories or degraded shielding; Poor ground connection for the sensor or controller

DTC codes / P0Axx · Hybrid propulsion / P0A21

P0A21Motor Torque Sensor Circuit Intermittent

Q: What does code P0A21 mean?

Motor Torque Sensor Circuit Intermittent. P0A21 indicates that the hybrid or electric vehicle controller has detected an intermittent fault in the motor torque sensor circuit, meaning the signal from the sensor that measures electric motor output torque is dropping out or glitching. The computer sets this code when the sensor signal is momentarily lost or erratic, but not continuously failed, so the fault may not be present at the time of diagnosis.

P0A21 indicates that the hybrid or electric vehicle controller has detected an intermittent fault in the motor torque sensor circuit, meaning the signal from the sensor that measures electric motor output torque is dropping out or glitching. The computer sets this code when the sensor signal is momentarily lost or erratic, but not continuously failed, so the fault may not be present at the time of diagnosis.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the hybrid system warning light or service vehicle soon light
Intermittent loss of power or hesitation during acceleration
The vehicle may enter a reduced power or limp mode
Rough running or shuddering under load
Often no symptoms besides the warning light, especially if the fault is very brief

Common causes, most likely first

Loose, corroded, or damaged electrical connector at the motor torque sensor
Chafed or broken wiring in the motor torque sensor circuit
Failing motor torque sensor
Faulty hybrid vehicle control module or inverter assembly
Electromagnetic interference from aftermarket accessories or degraded shielding
Poor ground connection for the sensor or controller

How to diagnose and fix it

Perform a visual inspection of the motor torque sensor and its wiring harness for obvious damage, corrosion, or loose connections
Check for technical service bulletins (TSBs) related to the code and vehicle model
Use a scan tool to monitor live data from the motor torque sensor while wiggling connectors and harnesses to reproduce the intermittent fault
Measure resistance and continuity of the sensor circuit from the sensor to the controller, looking for opens or shorts
If the sensor is accessible, test its output signal with an oscilloscope to verify a clean waveform
Replace the motor torque sensor if faulty, following the manufacturer's procedure
If the sensor and wiring are good, diagnose or replace the hybrid control module or inverter as required

Intermittent faults demand patience and live data

An intermittent code like P0A21 often leaves no stored freeze-frame data, so you must rely on live sensor readings and wiggle tests to catch the fault in the act.
A common oversight is replacing the motor torque sensor without first checking the connector pins for slight push-back or corrosion that only breaks contact under vibration.
The code can be set by a momentary voltage spike or drop from a failing 12-volt battery or charging system, so always verify battery and charging system health before condemning hybrid components.
Aftermarket electrical accessories or poor grounding can introduce noise into the sensor circuit, causing false intermittent signals that mimic a failing sensor.
On some vehicles, the motor torque sensor is integrated into the motor assembly and not serviceable separately, requiring replacement of the entire motor unit.

Can I keep driving with P0A21?

You can generally continue driving to a repair shop, but avoid heavy acceleration or high-speed driving because a sudden loss of torque signal could cause the vehicle to enter limp mode without warning. If the warning light flashes or the vehicle repeatedly loses power, stop driving and have it towed.

Tools that help

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