BYD ATTO 3 (e-Platform 3.0) P1BC100 Front Drive Motor Resolver Signal Amplitude Reduced

P1BC100 indicates that the front drive motor controller has detected a reduced or weakened resolver signal amplitude. The resolver provides rotor-position information to the motor controller, and insufficient signal amplitude can prevent the controller from accurately determining motor position. This may result in torque limitation, reduced drive performance, or protective shutdown of the electric drive system. BYD diagnostic references specifically identify P1BC100 as a front drive motor resolver fault involving weakened signal amplitude.

Symptoms

• Electric-drive or powertrain warning appears
• Reduced motor power or torque
• Poor or inconsistent acceleration
• Vehicle may enter a protective operating mode
• Regenerative braking may be reduced or disabled
• Motor operation may become intermittent
• Vehicle may fail to enter READY mode
• Electric-drive operation may be disabled in severe cases
• Rotor-position data may become unstable or implausible
• Additional resolver or motor-controller DTCs may be stored

Possible Causes

• Weak or deteriorated front motor resolver signal
• Damaged resolver
• Resolver excitation or signal-circuit fault
• Open circuit or high resistance in resolver wiring
• Loose or poorly seated connector
• Corroded, damaged, or contaminated connector pins
• Damaged motor wiring harness
• Electrical interference affecting the resolver signal
• Fault within the front drive motor assembly
• Motor-controller resolver decoding circuit fault
• Incorrect motor resolver zero-position calibration

Diagnosis

Diagnosis should begin by confirming P1BC100 and checking for related resolver and front motor-controller DTCs. Particular attention should be given to P1BBF00, which indicates resolver signal loss, and P1BC000, which indicates an abnormal resolver angle. BYD diagnostic references group these three codes together as front drive motor resolver faults.

Inspect the resolver connector, terminals and wiring for looseness, corrosion, damage, moisture intrusion or excessive resistance. The resolver signal circuits should then be tested against the manufacturer’s specifications, with diagnostic data used to monitor resolver amplitude and rotor-position information.

A documented BYD resolver fault investigation involving P1BBF00 and P1BC100 found that checking the resolver connector, pins, motor assembly and rear-cover sealing condition was an important part of the diagnostic process.

If the wiring and connectors are satisfactory, the resolver itself and the motor-controller resolver decoding circuit should be investigated. Published BYD diagnostic research identifies resolver damage, resolver wiring faults, connector problems, drive-motor assembly faults, motor-controller decoding faults and incorrect drive-motor zero-position calibration as potential causes of resolver-related DTCs.

For New Zealand owners, confirming resolver signal quality, wiring and calibration before replacing the complete drive motor or motor controller can help avoid unnecessary repair costs.

Because this fault involves the motor’s rotor-position feedback system, diagnosis should follow BYD’s prescribed procedures and use appropriate diagnostic equipment. Access to the factory service manual is particularly useful for resolver wiring diagrams, connector pinouts, signal specifications, resistance values and calibration procedures.

Applicable Years

2022, 2023, 2024, 2025, 2026, onwards