P0C08Drive Motor B Phase U-V-W Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0C08 is the open-phase check for drive motor B, the motor B twin of P0C05. GM runs it on the 2011 Volt and the 2012 two-mode trucks: each phase is checked as the rotor passes its axis, and a phase axis current below 9 A while at least 23 A is commanded, with the rotor within 30 degrees and over 35 V on the inverter, counts as a miss. Around 200 failed samples set it, Type A, one trip. Later GM tables up to 2016 keep the same logic. GM's eAssist has only one machine and no P0C08. The usual causes are a loose three-phase terminal, an open stator winding or an inverter stage that does not conduct. Motor B then delivers no torque, the MIL lights and drive power is reduced.
- What you may notice
- Malfunction indicator lamp after one drive
- Reduced propulsion power
- Engine running more often than usual
- Likely causes
- LikelyLoose or open three-phase terminal between inverter and motor B
- PossibleOpen stator winding in drive motor B
- PossibleInverter stage for motor B not conducting
- 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: €100 – €5,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.