P0C09 code meaning
Drive Motor B Phase U-V-W Circuit Low
Powertrain system Generic code P0Cxx codes Check engine light
What P0C09 means
P0C09 marks a U, V or W phase line of drive motor B that is pulled low, for example by a short to the negative high-voltage rail, to ground or by a power switch that conducts when it should not. It is the motor B twin of P0C06; the siblings P0C08 and P0C0A cover an open phase and a phase stuck high. No manufacturer documents P0C09 publicly, and GM's hybrid tables use only P0C08 for motor B phase circuits. CARB requires circuit fault monitoring of hybrid components. A low phase usually causes overcurrent too, so P0C04 or insulation codes often accompany it. The motor controller switches motor B off; the vehicle continues with reduced power and a warning lamp.
P0C09 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 10 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0C09
- Motor B shut down with warning lamp
- Overcurrent or insulation codes stored at the same time
Common causes of P0C09
- PossiblePhase cable or winding of motor B shorted to ground or housing
- PossibleShorted low-side power switch in the motor B inverter
- Less likelyInsulation damage from heat, moisture or chafing
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 uvwDrive motor b inverter
What each part of P0C09 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 09 | The exact fault in that area. |
What to do next
- Note P0C09 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 P0C09
What does P0C09 mean?
P0C09 means "Drive Motor B Phase U-V-W Circuit Low". P0C09 marks a U, V or W phase line of drive motor B that is pulled low, for example by a short to the negative high-voltage rail, to ground or by a power switch that conducts when it should not. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C09?
Drive gently and only to a workshop. With P0C09 the car can go into limp mode (reduced power) to protect itself.
Will P0C09 fail an emissions test?
Yes, it can. P0C09 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 P0C09 to fix?
Difficulty: workshop only. A typical repair takes 1 to 10 hours of work. This is a job for a workshop.
Will P0C09 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.