P0BF9 is reserved for a general circuit fault of the phase W current sensor in the drive motor B inverter, outside the offset, low and high categories that have their own codes. No manufacturer documents this exact code publicly; GM's tables from the 2011 Volt through 2019, and Jeep's 2020 Renegade and Compass PHEV bulletins, refer only to the specific siblings, chiefly P0BFA. CARB requires hybrid sensor circuits to be monitored. If the controller cannot trust phase W of motor B, it can no longer close the three-phase current balance checked by P0BFE and therefore limits or disables that motor. The sensor sits inside the inverter, so repair usually means replacing the inverter assembly.
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
- Hybrid system warning and malfunction indicator lamp
- Reduced power or no contribution from drive motor B
Most likely causes
- Failed phase W current sensor in the motor B inverter
- Supply or signal fault on the inverter's sensor board
- Software fault in the motor B control processor
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0BF9 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- F9: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0BF9?
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 P0BF9?
The most common causes are: failed phase W current sensor in the motor B inverter; supply or signal fault on the inverter's sensor board; software fault in the motor B control processor.
Related codes
- P0BFADrive Motor B Phase W Current Sensor Circuit Range/Performance
- P0BFBDrive Motor B Phase W Current Sensor Circuit Low
- P0BFCDrive Motor B Phase W Current Sensor Circuit High
- P0BF1Drive Motor B Phase U Current Sensor Circuit
- P0BF5Drive Motor B Phase V Current Sensor Circuit
- P0BEDDrive Motor A Phase W Current Sensor Circuit
- P0BFEDrive Motor B Phase U-V-W Current Sensor Correlation
- P0C08Drive Motor B Phase U-V-W Circuit/Open
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 16OBDG02 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.