P0BF2: Drive Motor B Phase U Current Sensor Circuit Range/Performance

What it means

The current sensor for drive motor B phase U reports a circuit range/performance fault. Phase current measurement is unreliable.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

The inverter uses the drive motor B phase U current sensor to measure current in that specific motor phase. This code sets when its signal is outside the expected range or response, such as from sensor offset drift, so the module may restrict motor output.

Common causes

Most likely first.

1. Current sensor offset drifted
2. Magnetic offset
3. Sensor element aged beyond calibration window

Symptoms

• EV/hybrid system warning light on
• Reduced motor power or torque
• Possible limp mode or vehicle shutdown

How to diagnose it

1. Capture freeze-frame data and monitor live drive motor B phase U current values to check for a steady offset or an abnormal response compared with phases V and W.
2. With the high-voltage system made safe according to the manufacturer's procedure, inspect the phase U sensor and connector for damage, corrosion, loose pins, or magnetic material near the sensor.
3. Check the phase U sensor signal, supply, and ground connections for poor contact or wiring interference using the manufacturer's wiring information.
4. Compare phase U readings with drive motor B phases V and W during equivalent operating conditions to confirm whether the range/performance issue is specific to U.
5. If external causes and wiring faults are ruled out, test phase U sensor offset and response against the manufacturer's specification.

Common fixes

• Clean and secure the drive motor B phase U sensor connector.
• Repair a poor connection or damaged wiring in the phase U sensor circuit.
• Remove external magnetic interference near the phase U sensor if found and applicable.
• Replace the drive motor B phase U current sensor if its offset or response remains outside specification.

Can I keep driving?

Avoid high-demand driving if torque is reduced or limp mode is active, since the system may further limit or disable drive motor B. Stop safely if a shutdown warning appears or the vehicle loses drive.