B1C1371 - Trunk Lock Motor Stall

B1C1371 Trunk Latch Motor Stall

Fault Definition

In vehicle intelligent electronic architecture systems, fault code B1C1371 is specifically used to identify the abnormal state of the Electric Back Door Lock system. The core logic of this code lies in monitoring the motor's load feedback signal. When the control unit sends an open or close command to the electric back door lock motor, the system is in a typical load feedback loop. Under normal conditions, the motor should exhibit linear drive characteristics; however, when physical resistance exceeds the threshold or internal execution mechanisms jam, causing current to significantly deviate from the expected safe range, the system judges it as "Stall". This definition emphasizes the control unit's protective monitoring of motor working status, ensuring prevention of hardware overheating or electrical component overload damage under abnormal high-load conditions.

Common Fault Symptoms

Based on the trigger logic of this fault code, car owners may perceive the following specific phenomena in actual driving experiences:

• Electric Back Door Lock Failure: After pressing the remote key lock command, the trunk cannot automatically close; or when unlocking the vehicle, the back door cannot open normally.
• Actuator No Response: Using the back door open button next to the interior dome light switch or physical mechanical switch, the system prompts that the motor is not rotating.
• Instrument Warning: Some models display relevant door/trunk fault indicator lights on the central information screen or combination instrument cluster when detecting such circuit load abnormalities.
• Limited Function Mode: After reading historical data via the vehicle diagnostic interface, it may be found that the actuator has entered a protective hibernation state until the fault code is cleared and the system reset.

Core Fault Cause Analysis

The causes of this fault can mainly be summarized into technical logic abnormalities in the following three dimensions:

1. Hardware Component Level: The core lies in internal mechanical jamming, gear mechanism fracture or motor drive coil aging occurring in the electric back door lock execution unit itself, resulting in an inability to maintain a low current rotation state under commands.
2. Wiring and Connector Level: Includes supply circuit impedance abnormalities (such as wire harness damage causing short circuits to ground); or high contact resistance caused by connector pin oxidation/loosening, interfering with the control unit's accurate collection of load signals.
3. Controller Logic Level: Involves the internal drive chip failure of the Rear Domain Controller, or deviation in its built-in current sampling module, mistakenly identifying normal start-stop processes as high load states.

Technical Monitoring and Trigger Logic

The control system judges the specific boundary conditions of this fault according to strict electrical parameters, with the logic flow as follows:

• Specific Operating Condition Limitations: The prerequisite for fault judgment is When the trunk latch lock is working. The system evaluates motor current only during the dynamic monitoring process after this execution command is activated; current fluctuations under static standby status are not included in this fault logic judgment.
• Monitor Target Signals: The control unit collects feedback current values and voltage waveforms in real-time within the electric back door lock drive circuit, focusing on analyzing instantaneous change rates of load signals.
• Numerical Threshold Judgment: The system sets clear current safety boundaries. Once the monitored control circuit current reaches or exceeds $ \ge 5A $ for a certain duration, protective interrupt logic is triggered. This value $ 5A $ serves as a key physical quantity threshold for Stall determination, used to distinguish between normal startup peak and abnormal sustained high flow under fault conditions.