C11B372 - C11B372 Right Motor Drive MOSFET Voltage Abnormality

Deep Definition of Fault for Abnormal MOSFET Drive Voltage on Right Motor Driver C11B372

In this vehicle electronic system architecture, fault code C11B372 represents the diagnostic result of the internal critical power control circuit within the Electronic Parking Brake System (EPB). This fault is defined as "Abnormal MOSFET Drive Voltage on Right Motor," involving the Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET) acting as a core power switch element for driving the motor. In system logic, the electronic parking controller confirms the electrical connection integrity of the motor actuator by monitoring the drive voltage status across the MOSFET. When the control unit detects that the actual operating voltage of the MOSFET in the circuit path used for real-time feedback of motor physical position and rotation speed deviates from preset baseline values or is in an unexpected fluctuation state, the system determines this as "Voltage Abnormality." This concerns not only the motor start/stop logic but also directly relates to the electrical load capacity of the right rear caliper when executing parking commands. This definition clarifies that the fault lies within the monitoring closed loop of the Electronic Control Unit (ECU) on the actuator output end, belonging to diagnostic information at the driver side hardware or control logic level.

Common Fault Symptoms

When fault code C11B372 is triggered during vehicle operation, users may observe the following specific manifestations in driving experience or instrument cluster interaction:

• Instrument System Alarm: With the ignition switch in work mode, the Electronic Parking Brake warning lamp on the driver's instrument cluster may light up and flash along with the fault indicator.
• Right Rear Caliper Function Failure: When executing parking or release operations, the electric motor brake corresponding to the right rear wheel cannot act normally, manifesting as a mechanical "locking" state that cannot be released by electrical instructions.
• System Log Recording: The On-Board Diagnostics (OBD) system records this specific fault code in the background, indicating that the control unit has confirmed abnormal electrical signal characteristics in the right rear drive circuit.
• Parking Performance Risk: Due to restricted release of the right side brake, it may lead to an inability to fully lock wheels when parked or result in a unilaterally lagging response when releasing parking commands while driving.

Core Fault Cause Analysis

According to diagnostic data, the root cause of this fault can be categorized into hardware or logic issues in the following three dimensions:

• Electronic Parking Controller Failure: The gate driver circuit inside the control unit responsible for generating MOSFET drive signals may be damaged, causing abnormal output pulses; or there may be logic drift in the voltage monitoring circuit (such as ADC sampling module) inside the controller, erroneously triggering the fault code.
• Right Rear Caliper Motor Failure: The DC brushless motor winding inside the right rear brake caliper undergoes short circuit, open circuit, or internal coil aging, directly causing nonlinear impedance characteristics at the motor drive terminal when powered on, leading to the monitored voltage across the MOSFET exceeding the normal linear region.
• Wiring and Connector Issues (Potential Associated Factors): Although the fault code does not explicitly mark a line disconnection, within hardware components, high-voltage harnesses on the motor side may have ground short circuits, leakage caused by worn insulation layers, or abnormally high contact resistance at connectors causing voltage drops, all of which may lead the control unit to interpret as voltage abnormality.

Technical Monitoring and Trigger Logic

This system establishes strict real-time monitoring mechanisms for driver circuit status, with its determination process following specific working conditions and parameter threshold logic:

• Monitoring Target: The system primarily monitors the drive voltage signals between MOSFET pins (gate, source, or drain) in the right rear caliper motor driver.
• Trigger Conditions: The necessary premise for fault determination is the Start switch placed in ON gear. The control unit needs to initialize each subsystem after ignition cycle completion and perform self-checks on the electrical status of the electronic parking system with ignition on.
• Logic Judgment Process: During motor drive activation, the controller samples MOSFET voltage values in real time. If the monitored voltage value continues to be below the minimum working threshold or above the maximum safety threshold, the system will immediately mark it as "Voltage Abnormality." This fault trigger belongs to the dynamic monitoring category, meaning the system pays attention not only to static connections but also to voltage stability and load matching during electrical signal transmission. Once the above logic combination is met, ECU will write DTC C11B372 to mark circuit state failure.