BYD ATTO 3 (e-Platform 3.0) P1BC300 Front Drive Motor Missing Phase B

P1BC300 indicates that Phase B of the front drive motor is not being detected correctly. The fault is detected when the front drive motor controller identifies an abnormal or missing Phase B current or phase-drive condition, potentially causing torque limitation or protective shutdown of the electric drive system. The BYD ATTO 3 uses the e-Platform 3.0 architecture and a permanent-magnet synchronous front drive motor, with the controller monitoring the three-phase motor circuit during propulsion and regenerative operation. BYD diagnostic information specifically identifies P1BC300 as a missing Phase B fault in the front drive motor.

Symptoms

• Reduced drive power or motor torque
• Powertrain or electric-drive warning appears
• Acceleration may become limited
• Vehicle may enter a protective operating mode
• Regenerative braking may be reduced or disabled
• Motor operation may become intermittent
• Vehicle may refuse to enter READY mode
• Electric-drive operation may be disabled in severe cases
• Multiple motor-controller DTCs may be stored
• Fault may occur during acceleration or high-load operation

Possible Causes

• Open circuit in the Phase B motor circuit
• Damaged Phase B high-voltage wiring
• Loose or poorly seated motor connector
• Poor contact or damaged Phase B terminals
• Phase B winding fault inside the drive motor
• Phase-to-phase short circuit
• Motor insulation fault
• Front drive motor controller power-stage fault
• IGBT or IPM malfunction
• Current Hall-sensor fault affecting Phase B detection
• High resistance in the Phase B circuit
• Internal motor-controller hardware failure

Diagnosis

Diagnosis should begin by confirming P1BC300 and checking for related Phase A or Phase C missing-phase codes, motor overcurrent, IPM, IGBT, Hall-sensor, high-voltage and communication DTCs. Diagnostic attention should then focus on Phase B current data, three-phase current balance, motor-controller output, high-voltage connections, motor connector condition, and the integrity of the Phase B circuit. BYD diagnostic information identifies P1BC200 and P1BC400 as the corresponding Phase A and Phase C missing-phase faults, while P1BC500, P1BC600 and P1BC900 relate to the motor controller’s current Hall sensors.

For New Zealand owners, confirming the Phase B circuit and motor-controller connections before replacing the drive motor or inverter assembly can help avoid unnecessary repair costs.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, connector pinouts, specifications, and system calibration information. Access to the factory service manual significantly reduces diagnostic time and helps prevent unnecessary parts replacement.

To order the correct OEM Service and Repair Manual for your BYD ATTO 3, submit your request using the form below and our team will provide the ordering details.

Applicable Years

2022, 2023, 2024, 2025, 2026, onwards

To order the correct OEM Service and Repair Manual for your BYD ATTO 3, submit your request using the form below and our team will provide the ordering details.