P0C09Drive Motor B Phase U-V-W Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Motor B shut down with warning lamp
- Overcurrent or insulation codes stored at the same time
- Likely causes
- PossiblePhase cable or winding of motor B shorted to ground or housing
- PossibleShorted low-side power switch in the motor B inverter
- RareInsulation damage from heat, moisture or chafing
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €200 – €6,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.