Powertrain, generic · Hybrid propulsion
P0A21 Motor Torque Sensor Circuit Intermittent
Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible
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.
Likely causes
Loose or fretted terminal in the sensor connector
Chafed sensor wiring that shorts briefly under vibration
Damaged shield letting inverter noise into the signal
Symptoms
- Hybrid warning that appears and disappears
- Brief loss of electric assist
Repair estimate
DifficultyHardWorkshop job
Parts and labour€100–3,000
Time1–8 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
motor torque sensorwiring harnesshybrid control module
Related codes
References: patents.google.com, law.cornell.edu.