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Powertrain Source reviewed Lights the check engine lamp

P0BFB: Drive Motor B Phase W Current Sensor Circuit Low

Standardized SAE J2012 code · P0Bxx — Hybrid and electric propulsion

Safety-critical system. Faults in airbags, brakes, steering or high-voltage components can put people at risk. Follow the manufacturer's service information and safety procedures, or have the vehicle checked by a qualified workshop.

What does P0BFB mean?

P0BFB indicates that the phase W current sensor of the motor B inverter delivers a signal below its valid range. GM's limits: below -800 A on the 2011 Volt (Type A, 4 of 6 samples at 10.4 ms), below -700 A on the 2012 and 2013 two-mode trucks (Type B, two trips) and below -700 A for 0.05 of 0.1 s in the 2016 tables or 0.1 of 0.15 s in a 2019 table (Type A, one trip). The threshold lies well outside any phase current motor B can carry, so the likely cause is a sensor output stuck near ground, a failed sensor or a supply fault on the sensor board. P0BFA covers a shifted zero, P0BFC the high side. While the code is active, motor B delivers reduced or no torque.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

  • Malfunction indicator lamp and hybrid warning
  • Reduced power or no contribution from drive motor B

Common causes

  • High Failed phase W current sensor in the motor B inverter
  • Medium Sensor signal or supply pulled to ground on the sensor board
  • Low Poor contact at an internal or external inverter connector

Likelihood is a general estimate across vehicles; your make and model may differ.

Add your car to see reports of P0BFB on the same make and model first.

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