P0BF4: 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. 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.

Symptoms

• Malfunction indicator lamp and hybrid warning
• Reduced power from drive motor B
• Further inverter or phase current codes stored

Most likely causes

• Failed phase U current sensor in the motor B inverter
• Sensor signal shorted to the sensor supply voltage or open reference ground
• Poor contact at an internal or external inverter connector

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. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
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 P0BF4 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• F4: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0BF4?

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 P0BF4?

The most common causes are: failed phase U current sensor in the motor B inverter; sensor signal shorted to the sensor supply voltage or open reference ground; poor contact at an internal or external inverter connector.

Related codes

• P0BF3Drive Motor B Phase U Current Sensor Circuit Low
• P0BF1Drive Motor B Phase U Current Sensor Circuit
• P0BF2Drive Motor B Phase U Current Sensor Circuit Range/Performance
• P0BF8Drive Motor B Phase V Current Sensor Circuit High
• P0BFCDrive Motor B Phase W Current Sensor Circuit High
• P0BE8Drive Motor A Phase U Current Sensor Circuit High
• P0BFEDrive Motor B Phase U-V-W Current Sensor Correlation
• P0C04Drive Motor B Current High

Sources

• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
• gsi.ext.gm.com: 12OBDG06 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.