BYD ATTO 3 (e-Platform 3.0) P1BC400 Front Drive Motor Missing Phase C

P1BC400 indicates that Phase C 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 C 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.

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 C motor circuit
• Damaged Phase C high-voltage wiring
• Loose or poorly seated motor connector
• Poor contact or damaged Phase C terminals
• Phase C 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 C detection
• High resistance in the Phase C circuit
• Internal motor-controller hardware failure

Diagnosis

Diagnosis should begin by confirming P1BC400 and checking for related Phase A or Phase B missing-phase codes, motor overcurrent, IPM, IGBT, Hall-sensor, high-voltage and communication DTCs. Diagnostic attention should then focus on Phase C current data, three-phase current balance, motor-controller output, high-voltage connections, motor connector condition, and the integrity of the Phase C circuit.

The corresponding missing-phase DTCs are P1BC200 for Phase A and P1BC300 for Phase B. P1BC500, P1BC600 and P1BC900 relate to the front motor controller’s current Hall-sensor circuits. Checking whether these codes are present together can help determine whether the problem is isolated to Phase C or originates from the controller’s current-sensing or power-stage circuitry.

For New Zealand owners, confirming the Phase C circuit, motor connector, and controller output 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.