P0A91
Drive Motor B Performance
The drive motor B does not deliver the expected torque or efficiency. Phase imbalance, magnet weakness, or bearing wear.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- EV/hybrid system warning light on
- Reduced motor power or torque
- Possible limp mode or vehicle shutdown
Common causes
Ordered by how often each turns out to be the cause.
- Phase current imbalanceCommon
- Magnet flux degradedPossible
Parts involved
- Drive Motor B
P0A91 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.