P0A1C: Drive Motor B Control Module Performance

P0A1C is the counterpart of P0A1B for the second electric machine, drive motor B, and reports that its control processor is no longer trustworthy. GM hybrid tables use it for the motor control processor B: in 2016 calibrations the code sets when an inhibit path test at power-down fails three or more times, in 2011 calibrations internal processor integrity faults such as SPI, RAM or cache errors are counted. Both are Type A with MIL on the first trip. The code concerns the control electronics, not a phase current sensor; those faults use their own codes. Expect a hybrid warning and loss of the affected motor function.

Symptoms

• Hybrid warning and MIL
• Reduced drive power or no electric drive

Most likely causes

• Internal processor or memory fault on the motor B control board
• Calibration or software fault in the inverter
• Unstable 12 V supply or ground to the inverter electronics

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. Compare the reading with other engine data while varying the engine speed.
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 P0A1C means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• A: Hybrid or air and fuel
• 1C: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A1C?

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 P0A1C?

The most common causes are: internal processor or memory fault on the motor B control board; calibration or software fault in the inverter; unstable 12 V supply or ground to the inverter electronics.

Related codes

• P0A1BDrive Motor A Control Module Performance
• P0A79Drive Motor B Inverter Performance
• P0A1DHybrid/EV Powertrain Control Module A
• P0A1AGenerator Control Module

Sources

• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
• law.cornell.edu: 13 CCR 1968.2

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.