P0A91 code meaning
Drive Motor B Performance
Powertrain system Generic code P0Axx codes Check engine light
What P0A91 means
P0A91 is set when the second electric drive motor (motor B) of a hybrid or electric vehicle does not deliver the expected speed or torque, although no electrical circuit fault is detected. Motor B exists only on systems with two traction motors, such as power-split or dual-motor layouts. CARB requires hybrid OBD systems to monitor electric motor performance. No manufacturer documents this code publicly; GM's tables describe the motor A equivalent P0A90 as a comparison between motor speed and a reference speed, which illustrates the approach. Causes range from inverter or resolver faults to mechanical damage. The vehicle usually limits power or enters a reduced mode. P0A79 covers inverter B performance.
P0A91 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0A91
- Hybrid/EV system warning and MIL
- Reduced power or limp mode
Common causes of P0A91
- PossibleInverter B fault limiting motor current
- PossibleMotor position sensor (resolver) signal error
- Less likelyMechanical damage to motor B or its gearing
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Drive motor b
What each part of P0A91 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A | Area: hybrid propulsion. |
| 91 | The exact fault in that area. |
What to do next
- Note P0A91 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0A91
What does P0A91 mean?
P0A91 means "Drive Motor B Performance". P0A91 is set when the second electric drive motor (motor B) of a hybrid or electric vehicle does not deliver the expected speed or torque, although no electrical circuit fault is detected. It is a generic code, so it means the same on every make.
Is it safe to drive with P0A91?
Drive gently and only to a workshop. With P0A91 the car can go into limp mode (reduced power) to protect itself.
Will P0A91 fail an emissions test?
Yes, it can. P0A91 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0A91 to fix?
Difficulty: workshop only. A typical repair takes 1 to 8 hours of work. This is a job for a workshop.
Will P0A91 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.