Powertrain, generic · Hybrid propulsion

P0A55 Drive Motor B Current Sensor Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0A55 is the general circuit fault of the current sensor that measures the current of drive motor B, typically the second traction motor, for example on a rear axle. The inverter needs this signal for torque control and to protect its power switches. No manufacturer documents P0A55 publicly. A Toyota patent shows the principle behind such checks: a control sensor and a monitoring sensor watch the same motor current, and a sensor stuck in its ground-short range or a lasting gap between the two leads to the relays opening. CARB requires circuit checks of hybrid input components. P0A56 is plausibility, P0A57/P0A58 low and high; P0A51 is the same fault on motor A. Usually drive motor B is switched off and the car drives on reduced power.

Likely causes

Current sensor of drive motor B failed (usually inside the inverter)
Sensor supply or signal line interrupted or shorted
Evaluation circuit on the motor B control board faulty

Symptoms

  • Hybrid or electric drive warning with MIL
  • Drive motor B disabled, loss of electric all-wheel drive or reduced power

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€300–4,500
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

drive motor b current sensorwiring harnesshybrid control module

Related codes

P0A56P0A57P0A58P0A51P0A79

References: patents.google.com, patents.google.com, law.cornell.edu.