Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble getting a steady signal from the sensor that tells it how much power the electric motor is using. It's like trying to watch a TV show with a bad signal – the picture keeps cutting in and out.
The P0A21 code is triggered when the powertrain control module (PCM) or hybrid control module detects an intermittent issue in the motor torque sensor circuit. This sensor is crucial for monitoring and controlling the electric motor's output.
The motor torque sensor is responsible for providing real-time data on the torque output of the electric motor. An intermittent circuit issue indicates that the signal from this sensor is not stable, which can affect the performance and efficiency of the hybrid system. The PCM relies on this data to manage power distribution between the electric motor and the internal combustion engine.
• Check Engine Light illuminated
• Reduced fuel efficiency
• Unusual noises from the electric motor
• Faulty motor torque sensor
• Damaged or corroded wiring/connectors
• Faulty hybrid control module
PCM: Powertrain Control Module
Hybrid Control Module: A component that manages the hybrid system's operation
• Inspect the wiring and connectors for damage or corrosion.
• Test the motor torque sensor for proper operation.
• Check the hybrid control module for faults.
• Replace the motor torque sensor if faulty.
• Repair or replace damaged wiring/connectors.
• Replace the hybrid control module if necessary.
• OBD-II scanner
• Multimeter
• Wiring repair kit
$200 - $600
Moderate
• Toyota Prius
• Honda Insight
• Chevrolet Volt
• Regularly inspect and maintain wiring and connectors.
• Schedule periodic hybrid system check-ups.
• Avoid harsh driving conditions that may damage sensors.
Sensor Issue
• Drive gently to avoid further stress on the hybrid system.
• Schedule a diagnostic check with a professional mechanic.
Check with your vehicle manufacturer as hybrid components may have extended warranties.
This code has been more prevalent in vehicles with older hybrid systems due to wear and tear on sensors and wiring.
Moderate – While the vehicle may still be operable, efficiency and performance could be compromised.
Driving with a malfunctioning hybrid system can lead to increased emissions and reduced performance.
• Vehicle at operating temperature
• Hybrid system engaged
The motor torque sensor is typically located near the electric motor or integrated into the hybrid transmission assembly.
Q: Can I drive my car with a P0A21 code?
A: While you may be able to drive, it is not recommended as it can affect performance and efficiency.
Q: How can I prevent this code from appearing again?
A: Regular maintenance and inspections of the hybrid system and its components can help prevent this issue.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
View on Amazon
Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.