P0A91: Drive Motor B Performance
What to do
As P0A90: companion codes and a battery report before any motor is condemned. On an electric-rear-axle car, expect the all-wheel drive to be the casualty.
What this code means
The second drive motor is not delivering what was commanded.
P0A90's chain argument applies whole — the motor is the last link, and upstream weaknesses present here — with motor B's usual geography: on rear-motor cars the symptom is all-wheel drive fading or gone, and the underfloor cable run joins the suspect chain.
Likely causes
Start here
- Hybrid battery pack deterioration · specialist
Less common
- Faulty power inverter · specialist
- Damaged high voltage phase cable or terminal · specialist
- Motor winding insulation breakdown · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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