B1C4013 Four Door Lock Motor Open Circuit Fault Technical Specification Document

H2 DTC Identification and System Overview

DTC: B1C4013
Fault Name: Four Door Lock Motor Open Circuit
Involved Controller: Left Domain Controller
Monitored Object: Four Door Lock Motor Actuators

Fault Severity Definition

In vehicle electronic architecture, B1C4013 is a critical diagnostic code used to identify specific actuator circuit abnormalities within the body control network. This code indicates that the "Left Domain Controller" cannot detect the expected current path response when executing door lock commands. The term "Open Circuit" does not solely mean physical wire disconnection; rather, it refers to the moment the drive signal is issued, where the monitored load current falls below the system preset threshold or is completely missing. This fault code reflects a failure in Control Loop signal integrity, meaning the control unit failed to establish a normal actuator operation feedback loop. The system continuously monitors motor drive status and will immediately trigger storage of B1C4013 into the fault memory upon detecting current interruption outside of idle states, potentially illuminating the corresponding Malfunction Indicator Lamp (MIL) or recording it in the diagnostic interface.

Common Fault Symptoms

When DTC B1C4013 is written into the system, affected vehicle components will exhibit obvious functional abnormalities. Based on the original data of "Four Door Lock Motor Failure," drivers and passengers may perceive the following specific driving experiences or instrument feedback:

• Mechanical Locking Failure: Lock commands issued via physical key or remote signal yield no response, causing the car door to be unable to close and lock.
• Central Unlock Malfunction: When pressing the unlock button inside the vehicle or remotely triggering an unlock, the four-door electric actuators will not move at all.
• System Status Abnormal Feedback: The instrument panel or central screen may display prompts such as "Door Not Closed" or "Lock System Fault," and some models may show specific Body Control Unit self-check warnings after ignition.
• Safety Redundancy Function Limited: In extreme conditions such as collisions, the emergency unlock mechanism that should automatically pop out may fail to function normally due to motor current monitoring failure.

Core Fault Cause Analysis

Regarding the generation logic of the B1C4013 code, fault roots are primarily focused on hardware components, physical connections, and control logic from three dimensions. All analyses are based on the trigger condition of "No Current" detected by the system:

Hardware Component Abnormalities

• Four Door Lock Motor Internal Damage: Stator coil open circuit or rotor jamming causing drive failure. When the control unit sends drive voltage to the motor, internally burnt windings cannot form a loop, leading to the monitoring end reading zero current value.
• Actuator Mechanical Seizure: Although the motor is powered, no displacement occurs (e.g., gear stripping), which under certain protection strategies may be regarded as an open circuit state or judged as abnormal due to no load current change.

Wiring and Connector Connection Issues

• Harness Physical Breakage: Power positive or return negative wires from the control unit to the door lock motor exist breaks, insulation layer wear causing ground short circuit (if system logic judges overvoltage protection) or complete disconnection, making signal path interrupted.
• Connector Poor Contact: Pin looseness, corrosion, or terminal backing off of connectors between Left Domain Controller and motor results in very poor electrical conduction, current cannot pass, satisfying the "Control Loop No Current" judgment condition.

Controller Logic Operation Faults

• Left Domain Controller Drive Level Failure: Power transistor (e.g., MOSFET) damaged or drive circuit aged inside control unit, leading to inability to output effective switch signals to drive motor, resulting in external monitored current of 0.
• Monitoring Algorithm Abnormality: Logic error occurs in monitoring module responsible for calculating loop impedance inside controller, failing to correctly identify normal small start currents and misjudging them as open circuit faults.

Technical Monitoring and Trigger Logic

To precisely lock the aforementioned faults, the Left Domain Controller adopts specific dynamic monitoring strategies to determine B1C4013. Its determination process follows strict technical logic:

Monitoring Target

The system focuses on monitoring Control Loop Working Current ($I_{circuit}$) and voltage status at the drive output end. The aim is to verify whether the motor can carry expected load current during operation.

Specific Operating Conditions

Fault judgment trigger is strictly limited to the dynamic condition of Four Door Lock Work (During Door Lock Actuation). Only after the controller issues a clear lock or unlock command will it enter the monitoring window. If the vehicle is in standby state, even if the line breaks, this code will not light up immediately, demonstrating the system's ability to distinguish between static current and dynamic load.

Trigger Logic Thresholds

• Command Response Phase: When drive signal activates, the control unit expects normal load current to exist in the loop ($I_{expected} > I_{threshold}$).
• Fault Judgment Condition: If no current is detected in the control loop within the action cycle ($I_{measured} \approx 0A$) and duration exceeds preset time window, system confirms open circuit logic.

This monitoring strategy ensures that B1C4013 is recorded only when the motor attempts to work but fails to build an effective current path, effectively avoiding false alarms caused by momentary voltage fluctuations or start surges.