B1C4071 - B1C4071 Four Door Lock Motors Stall

Fault Depth Definition

DTC B1C4071 identifies as "Four-Door Lock Motor Stall," this diagnostic code plays a critical role in load protection and functional safety verification within the vehicle body electronic control system. In the vehicle electrical architecture, the door lock actuator serves as a linear electric actuator element, whose core function is to convert electrical energy into mechanical energy to achieve locking or unlocking actions of the lock body. When the control unit (Domain Controller) issues a drive command, the system evaluates motor status by monitoring loop current in real-time. "Stall" refers to the phenomenon where input current surges sharply due to inability to establish speed caused by excessive mechanical resistance, gear jamming, or abnormal load during attempted rotation. The establishment of this DTC aims to prevent motor winding overheating and damage due to prolonged overcurrent, and avoid battery systems from experiencing abnormal instantaneous high-load impacts, ensuring the stability and safety of the body control network.

Common Fault Symptoms

When DTC B1C4071 is recorded or stored, users typically perceive the following abnormal manifestations during actual driving experience:

• All Door Lock Failure: The electric lock actuators on all four vehicle doors simultaneously lose response capability, leading to inability to lock or unlock all doors via one-touch operation.
• Instrument System Feedback Abnormality: Fault indicator lights related to body safety may light up on the combination instrument panel, or the vehicle prompts communication or execution abnormalities in the door lock system when entering specific safety modes.
• Missing Mechanical Linkage: Even if the driver sends a request to close the door, the physical latch does not hear normal motor operation sounds, and the key cannot trigger electronic locking feedback signals via conventional methods.
• Central Remote Control Malfunction: Proximity or remote control commands from smart keys fail to trigger synchronous locking actions on the four-door system, leaving the vehicle security system in a non-normal open state.

Core Fault Cause Analysis

Based on the fault logic tree, code generation for B1C4071 primarily stems from potential failure points in three dimensions, and blind disassembly is strictly prohibited before specific locations are clearly identified:

• Hardware Component Failure: Mainly involves physical jamming of internal mechanisms within the motor body or gear group. For example, damage to reduction gears inside the door lock actuator, dried lubrication causing excessive frictional torque, leading the motor into an electrical "stall" state when attempting to overcome resistance. Additionally, right-front window control switch failure may serve as abnormal signal input sources, interfering with system logic judgment of door lock status or indirectly triggering abnormal drive load allocation.
• Wiring and Connector Physical Connection: Includes main harness insulation damage on the body control network causing short circuit to ground, or excessive contact resistance caused by terminal corrosion, withdrawal of pins at the door lock motor end. High impedance leads to misjudgment in current monitoring and may also affect output voltage stability on the controller side.
• Controller Logic Operation Failure: Involves abnormal internal control strategies or power output modules within the Left Domain Controller (Domain Controller). When the control unit cannot correctly parse motor feedback signals, or its internal drive circuits exist short-circuit risks, it will erroneously determine that the system is in a high-current state to trigger protective fault codes.

Technical Monitoring and Trigger Logic

The diagnostic system collects electrical parameters via the vehicle network in real-time and determines whether conditions for storing B1C4071 are met under specific operating windows:

• Monitoring Target: Control Loop Load Current (Control Loop Current).
• Numerical Threshold Range: The system sets a monitoring threshold where detected instantaneous or continuous current is greater than or equal to $20\text{A}$. The significance of this value is significantly higher than the rated operating current of door lock motors during normal operation, making it a hard indicator for judging "stall."
• Specific Trigger Operating Conditions: Fault determination is only valid when the vehicle ignition switch is in ON position (before engine start or during running) and four-door lock control commands are active. The system monitors current curves during the dynamic process of executing locking/unlocking actions; if current does not fall back to a reasonable range with speed change during execution cycle but remains above $20\text{A}$, the fault trigger condition is confirmed as met, ultimately generating DTC B1C4071 recorded in diagnostic data stream.