P0A66 code meaning
Drive Motor B Phase U Current
Powertrain system Generic code P0Axx codes Check engine light
What P0A66 means
P0A66 is the general fault code for the current in phase U of drive motor B, the second electric machine of a two-motor hybrid or an electric rear-axle motor. No manufacturer documents P0A66 publicly; GM, for instance, only uses the open-phase code P0A67 for this phase. The checks behind such a code are described in patents: a Caterpillar patent declares a phase sensor failed when the three phase currents no longer add up to roughly zero, and a Hyundai patent shows inverters that measure two phases and calculate the third. CARB requires circuit and rationality monitoring of electric drive components. P0A67 and P0A68 are the low and high variants, P0A69 and P0A6C cover phases V and W, P0A5D is the same code on motor A. Motor B is normally shut off.
P0A66 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1.5 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0A66
- Hybrid system warning and MIL
- Motor B switched off, less power or no electric all-wheel drive
Common causes of P0A66
- Most likelyPhase U current sensor of motor B failed (inside the inverter)
- PossiblePhase U high-voltage cable or terminal between inverter and motor B faulty
- PossibleInternal fault in the motor B power stage
- Less likelyWinding fault in phase U of drive motor B
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Drive motor b phase uInverter
What each part of P0A66 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. |
| 66 | The exact fault in that area. |
What to do next
- Note P0A66 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 P0A66
What does P0A66 mean?
P0A66 means "Drive Motor B Phase U Current". P0A66 is the general fault code for the current in phase U of drive motor B, the second electric machine of a two-motor hybrid or an electric rear-axle motor. It is a generic code, so it means the same on every make.
Is it safe to drive with P0A66?
Drive gently and only to a workshop. With P0A66 the car can go into limp mode (reduced power) to protect itself.
Will P0A66 fail an emissions test?
Yes, it can. P0A66 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 P0A66 to fix?
Difficulty: workshop only. A typical repair takes 1.5 to 8 hours of work. This is a job for a workshop.
Will P0A66 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.