P0C0B: Drive Motor A Inverter Power Supply Circuit/Open

P0C0B flags a lost or interrupted supply inside the motor A inverter. GM reads it from the IGBT module status: when the gate drive supply falls below its threshold, the module reports a bias fault; on eAssist the 5 V rail below 3.5 to 4.3 V or the 15 V rail below 10.4 to 12.6 V counts, with run/crank above 7 V. The 2012 trucks enable it between 9.5 and 18 V; the 2016 to 2019 tables need 0.002 to 0.168 s of fault within short windows, Type A, one trip. Mercedes applies the code to the high-voltage supply of the inverter in the belt starter-alternator of P3 hybrids (subtypes 16 and 17) and replaces that unit. Expect loss of electric drive or engine start.

Symptoms

• Malfunction indicator lamp after one drive
• Electric drive or motor generator unavailable
• Engine cannot be started, only electric driving possible (Mercedes P3 hybrids)

Most likely causes

• Failed gate-drive power supply inside the motor A inverter
• Low 12 V feed, blown fuse or poor ground to the inverter control board
• Open high-voltage feed to the inverter, e.g. in a belt starter-alternator (Mercedes LI15.40-P-077947)

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Check the continuity of the wire between the component and the control module.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0C0B means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• C: Subsystem depends on the code range
• 0B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0C0B?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0C0B?

The most common causes are: failed gate-drive power supply inside the motor A inverter; low 12 V feed, blown fuse or poor ground to the inverter control board; open high-voltage feed to the inverter, e.g. in a belt starter-alternator (Mercedes LI15.40-P-077947).

Related codes

• P0C0CDrive Motor A Inverter Power Supply Circuit Low
• P0C0DDrive Motor A Inverter Power Supply Circuit High
• P0C0EDrive Motor B Inverter Power Supply Circuit/Open
• P0A78Drive Motor A Inverter Performance
• P0BE6Drive Motor A Phase U Current Sensor Circuit Range/Performance
• P0BEADrive Motor A Phase V Current Sensor Circuit Range/Performance
• P0BEEDrive Motor A Phase W Current Sensor Circuit Range/Performance
• P0D2EDrive Motor A Inverter Voltage Sensor A Circuit Range/Performance

Sources

• gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics
• gsi.ext.gm.com: 13OBDG05C Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.