Powertrain, generic (extended)

P2E28 Drive Motor A Excitation Current Sensor Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2E28 concerns a drive motor with an electrically excited rotor, the type Nissan uses in the Ariya and BMW in its fifth-generation eDrive. Such a rotor carries a field coil that receives direct current through brushes and slip rings; a sensor measures that current for the closed field-control loop. P2E28 means the sensor signal is electrically valid but does not make sense, for instance it disagrees with a second sensor or with what the commanded duty cycle should produce. CARB wants rationality faults stored apart from circuit faults. No manufacturer documents P2E28 publicly, nor its thresholds. Wiring faults are P2E7B, P2E29 and P2E2A; a real overcurrent is P2E2B. Without a trusted reading the field cannot be regulated, so expect reduced or no drive power.

Likely causes

Excitation current sensor drifted (offset or gain no longer correct)
Faulty excitation power stage, so actual and expected current differ
Worn brushes or dirty slip rings changing the field circuit resistance
Inverter or motor control software fault

Symptoms

  • Electric drive warning or service message
  • Noticeably reduced drive power
  • Vehicle may refuse to drive or stop driving

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–4,000
Time1–6 h

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

Parts involved

drive motor a excitation current sensordrive motor a excitation circuithybrid control module

Related codes

P2E7BP2E29P2E2AP2E2BP0A78

References: ti.com, nissan-global.com, newsroom.bmwgroup.com, law.cornell.edu.