P0BF4 code meaning
Drive Motor B Phase U Current Sensor Circuit High
Powertrain system Generic code P0Bxx codes Check engine light
What P0BF4 means
P0BF4 is the upper-limit counterpart of P0BF3 for the phase U current sensor of drive motor B. GM's thresholds: above 800 A on the 2011 Volt, checked with PWM output disabled (Type A); above 700 A on the 2012 and 2013 two-mode trucks (Type B, two trips); above 700 A for 0.05 of 0.1 s in the 2016 tables and 0.1 of 0.15 s in a 2019 table (Type A, one trip). Because the test runs with the power stage idle or the value lies far beyond any real current, it points to the sensor, its supply or an open reference rather than to genuine overcurrent; GM reports real excess phase current of motor B separately under P0C04 (above 600 A in the 2016 and 2019 tables). Motor B output is limited until repair.
P0BF4 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0BF4
- Malfunction indicator lamp and hybrid warning
- Reduced power from drive motor B
- Further inverter or phase current codes stored
Common causes of P0BF4
- Most likelyFailed phase U current sensor in the motor B inverter
- PossibleSensor signal shorted to the sensor supply voltage or open reference ground
- Less likelyPoor contact at an internal or external inverter connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Drive motor b phase u current sensorWiring harnessHybrid control module
What each part of P0BF4 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B | Area: hybrid propulsion. |
| F4 | The exact fault in that area. |
What to do next
- Note P0BF4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0BF4
What does P0BF4 mean?
P0BF4 means "Drive Motor B Phase U Current Sensor Circuit High". P0BF4 is the upper-limit counterpart of P0BF3 for the phase U current sensor of drive motor B. It is a generic code, so it means the same on every make.
Is it safe to drive with P0BF4?
Drive gently and only to a workshop. With P0BF4 the car can go into limp mode (reduced power) to protect itself.
Will P0BF4 fail an emissions test?
Yes, it can. P0BF4 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0BF4 to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0BF4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.