P0A21 code meaning
Motor Torque Sensor Circuit Intermittent
Powertrain system Generic code P0Axx codes Check engine light
What P0A21 means
Here the torque sensor on the traction motor shaft delivers a signal that drops out or jumps for short moments instead of failing permanently. Such shaft sensors, as in the Honda patent with a sensor inside a hollow motor shaft, sit in an area with strong electromagnetic fields and vibration, so loose terminals, chafed wires and interference are the usual suspects. P0A21 sets when the control unit counts too many implausible signal changes. No manufacturer documents P0A21 publicly; CARB demands an approved drive motor monitor. Steady faults would show as P0A19 or P0A20. The warning may come and go.
P0A21 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0A21
- Hybrid warning that appears and disappears
- Brief loss of electric assist
Common causes of P0A21
- Most likelyLoose or fretted terminal in the sensor connector
- PossibleChafed sensor wiring that shorts briefly under vibration
- Less likelyDamaged shield letting inverter noise into the signal
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Motor torque sensorWiring harnessHybrid control module
What each part of P0A21 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A | Area: hybrid propulsion. |
| 21 | The exact fault in that area. |
What to do next
- Note P0A21 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0A21
What does P0A21 mean?
P0A21 means "Motor Torque Sensor Circuit Intermittent". Here the torque sensor on the traction motor shaft delivers a signal that drops out or jumps for short moments instead of failing permanently. It is a generic code, so it means the same on every make.
Is it safe to drive with P0A21?
Drive gently and only to a workshop. With P0A21 the car can go into limp mode (reduced power) to protect itself.
Will P0A21 fail an emissions test?
Yes, it can. P0A21 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0A21 to fix?
Difficulty: hard. A typical repair takes 1 to 8 hours of work. This is a job for a workshop.
Will P0A21 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.