P0B01 means the pump inverter sees almost no current in phase U of the auxiliary fluid pump motor, typically an open phase. GM documents the check for the Volt motor control processor (2016) and its hybrid tables of 2018 and 2019: with the drive state in Run, the inverter in normal PWM above 50 V and a squared current command above 5 A2 (2016) or 14.97 A2 (2018), the peak current on the U axis is compared while the rotor is within 30 degrees of it; below 1 A for 0.4 s of a 0.6 s window, the code sets as Type A, MIL on the first trip. On the 2014-15 Chevrolet Spark EV, GM bulletin PI1433 links P0B01, P0B04 or P0B07, Service Vehicle Soon and reduced propulsion to an unlatched pump connector. P0B04/P0B07 are phases V and W, P0B02 the high side.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- Service Vehicle Soon light and MIL
- Propulsion Power Reduced or Vehicle Speed Limited message
Most likely causes
- Pump motor connector not fully seated or latched (Chevrolet Spark EV)
- Open circuit in the phase U lead or terminal of the pump motor cable
- Phase U switch in the pump inverter not conducting
- Open winding of phase U in the pump motor
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 P0B01 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- 01: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0B01?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0B01?
The most common causes are: pump motor connector not fully seated or latched (Chevrolet Spark EV); open circuit in the phase U lead or terminal of the pump motor cable; phase U switch in the pump inverter not conducting.
Related codes
- P0B00Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current
- P0B02Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High
- P0B04Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current Low
- P0B07Electric/Auxiliary Transmission Fluid Pump Motor Phase W Current Low
- P0C20Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit/Open
- P0C27Electric/Auxiliary Transmission Fluid Pump A Motor Current Low
Sources
- gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 18OBDG01 Hybrid Diagnostics
- static.nhtsa.gov: MC 10113757 9999
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.