P0BF1

Code

Generic P — Powertrain

Drive Motor B Phase U Current Sensor Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 38 RU: 25

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Page language: EN

Causes

Open, short or high-resistance wiring in the Phase U current sensor harness
Corroded, loose or mis-seated connector at the current sensor or inverter/EMC
Failed current sensor (Hall-effect sensor or shunt amplifier)
Faulty inverter / motor controller power electronics or PCB sensor input
Intermittent contact caused by vibration or pin damage
Short to battery positive or ground in the sensor circuit

Symptoms

Malfunction Indicator Lamp (MIL) or warning light illuminated
Reduced drive power or torque-limited (limp) mode
Regenerative braking reduced or disabled
Drive motor fault messages displayed on dash or info screen
Possible unusual motor noise, vibration or asymmetric torque
DTC stored in hybrid/EV control modules, potential related codes

What to check

Read freeze frame and full DTC list with a capable scan tool and record live data for motor currents
Visually inspect connectors, wiring and protective sleeving for damage, corrosion, pin push-out or water intrusion
Check fuses, relays and low-voltage supply and ground(es) for the motor/inverter circuits
Backprobe the sensor connector and monitor the signal while commanding motor operation (observe safety procedures)
Perform wiggle test on harness while monitoring live current sensor signal and DTC status
Compare Phase U sensor reading to Phase V and W (other phases) under the same conditions

Signal parameters

Typical Hall-effect current sensor: approx. mid-rail (about 2.5 V) at zero current, varying ±1–2 V with load; actual mid-rail and sensitivity depend on vehicle design
Some systems use low-level shunt sense: small millivolt signal proportional to current (requires amplifier in inverter); expected mV/A depends on hardware
Signal should be stable with smooth changes corresponding to commanded motor torque; no open-circuit (OL) or hard short to battery/ground
Reference supply (Vref) commonly 5 V or vehicle logic supply; sensor ground should be close to module ground (low ohms)
When idle, no rapid oscillation or dropout; under load the three phase currents should be similar in magnitude and phase-shifted appropriately

Diagnostic algorithm

Safety first: follow HV isolation and PPE procedures for hybrid/EV systems. Disable high-voltage system before any physical repairs.
Use a scan tool to confirm P0BF1 and capture live parameters, freeze frame, and any related P0BF or motor codes.
Visually inspect wiring and connectors for motor B Phase U from sensor through inverter to control module; repair any damage.
Check low-voltage supply and ground to the inverter and the sensor interface; verify proper connector seating and pin condition.
Backprobe the Phase U sensor signal, reference and ground while performing a controlled motor command (or cranking sequence per service manual). Observe with a scope if available; look for expected mid-rail voltage, smooth changes with load and no shorts/opens.
Compare Phase U readings to Phase V and W. If Phase U differs significantly, isolate to harness/sensor or inverter input.
Perform continuity and resistance checks between sensor connector pins and the inverter/control module pin using wiring diagram; check for short to battery or chassis ground.
If wiring and connectors pass, consider swapping the sensor module (if serviceable) or replacing the motor/inverter assembly per manufacturer guidance.
If replacement is required, clear codes and test-drive to confirm failure is resolved. If code returns, capture new data and escalate to inverter/module replacement or manufacturer tech support.
If intermittent, monitor while recreating operating conditions (temperature, load, vibration) that produce the fault.

Likely causes

Damaged or corroded connector/harness between motor B and inverter
Failed Phase U current sensor on motor B
Short or open in the sensor signal, reference or ground circuit
Inverter/controller sensor input stage failure
Intermittent wiring fault revealed under load or vibration

Fault status

⚠️ Status

Drive Motor B Phase U Current Sensor Circuit — control module detected invalid, missing or out-of-range current sensor signal for motor B phase U. System may derate or enter limp mode.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4.0 hours