P0C55 is the general circuit code for the first pickup winding (Circuit A) of the resolver on the second traction motor. It applies when the motor B controller recognises a fault on that winding but cannot assign it to a low or high level. No manufacturer documents this code publicly. GM, which runs two motors in the Volt, ELR and the two-mode trucks, files motor B winding faults under P0C57 and P0C58 instead. Compared with P0A45, which reports the motor B angle signal as a whole, P0C55 narrows the search to one winding and its two wires. CARB requires such circuit faults to be detected separately from out-of-range faults. The result is usually a warning lamp and the loss of motor B for drive or charging.
High severity. Can I keep driving?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.
Symptoms
- Check engine lamp with hybrid system warning
- Motor B unavailable, reduced propulsion
- Engine may run more often because the second motor is offline
Most likely causes
- Open wire or loose terminal in the motor B Circuit A lines
- Damaged or corroded motor B resolver connector
- Defective first pickup winding in the motor B resolver
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0C55 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- C: Subsystem depends on the code range
- 55: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0C55?
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 P0C55?
The most common causes are: open wire or loose terminal in the motor B Circuit A lines; damaged or corroded motor B resolver connector; defective first pickup winding in the motor B resolver.
Related codes
- P0C56Drive Motor B Position Sensor Circuit A Range/Performance
- P0C57Drive Motor B Position Sensor Circuit A Low
- P0C58Drive Motor B Position Sensor Circuit A High
- P0C59Drive Motor B Position Sensor Circuit A Intermittent/Erratic
- P0C5FDrive Motor B Position Sensor Circuit B
- P0A45Drive Motor B Position Sensor Circuit
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
- en.wikipedia.org: Resolver (electrical)
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.