C111013 - C111013 Ignition Switch Line Fault

C111013 Ignition Switch Line Fault Diagnostic Technical Description

Fault Depth Definition

C111013 Ignition Switch Line Fault is a key diagnostic fault code in the Electronic Parking Brake System (EPB). This fault code indicates that the control unit detected abnormalities in electrical signal integrity or discrepancies in logical state associated with the ignition switch circuit during specific monitoring cycles.

In the technical architecture of this system, the rear domain controller is responsible for monitoring the input link of ignition signals. When the system determines an "Ignition Switch Line Fault", it signifies an interruption, short circuit, or voltage threshold deviation in the power distribution or signal transmission path connected to the electronic parking brake system. This involves not only physical verification of line connectivity but also validation of communication logic between control units and actuators within the vehicle electrical network (Chassis Network). This fault code directly reflects that the ignition switch signal failed to be properly conveyed to the brake control module, thereby triggering the system's safety protection mechanism.

Common Fault Symptoms

When DTC C111013 is stored and the vehicle is in an operational state, vehicle owners may observe the following instrument panel feedback or changes in driving experience:

• Parking Brake Warning Light Illuminated: The Electronic Parking Brake (EPB) indicator light or relevant warning icons on the dashboard remain illuminated, indicating electrical abnormalities to the driver.
• Limited Electronic Parking Function: Some vehicles may be unable to execute complete manual locking or unlocking commands; the system enters a "Safety Mode," retaining only basic mechanical emergency capability.
• Ambiguous Braking Status Indication: In automatic start-stop scenarios, the system may fail to correctly identify the parking release signal, leading to temporary disablement of driver assistance functions.

Core Fault Cause Analysis

According to fault mechanism diagnosis logic, the potential root causes for C111013 can be categorized into the following three technical dimensions:

• Hardware Component Power Integrity (Fuse Blown): A dedicated protective element supplying power to the ignition switch signal circuit or control unit reference voltage experiences an open-circuit failure. If the relevant fuse blows due to overcurrent, normal voltage transmission on the line is cut off, causing the controller to fail in reading a valid ignition signal level.
• Line Physical Connection Status (Harness or Connector Fault): Includes conductor breakage within the harness, insulation wear leading to ground/power short circuits, and contact impedance caused by terminal oxidation, loosening, or connector pin withdrawal. Such physical damage interferes with the integrity transmission of the ignition switch signal, causing the control unit to receive erroneous voltage fluctuations.
• Controller Logic Processing Anomaly (Rear Domain Controller Fault): The Analog-to-Digital Converter (ADC) or signal conditioning circuit inside the rear domain controller responsible for monitoring the ignition input signal experiences drift, or the controller's software logic encounters a deadlock while processing ignition state frame data. Even if external lines are normal, this fault code is triggered if the controller cannot correctly parse voltage levels into corresponding switch states.

Technical Monitoring and Trigger Logic

The determination of this fault code relies on real-time interaction between the vehicle network (such as LIN or CAN) and the chassis control module. The core monitoring logic is as follows:

• Monitoring Target: The control unit focuses primarily on signal voltage stability at the ignition switch input terminal, data frame integrity on the communication bus, and circuit continuity. The system performs real-time comparison by contrasting theoretical reference values with actual acquired values.
• Trigger Conditions: Fault determination is only valid under specific electrical states and must satisfy the condition of Ignition Switch Placed in ON Position. When the driver turns the key or presses the start button to bring the vehicle into the Ignition On mode, the controller activates the monitoring window for the ignition lines.
• Abnormality Judgment Criteria: During the period the Ignition Switch is placed in ON, if the control unit detects ignition signal voltage below the safety threshold $V_{min}$ (referencing system minimum operating voltage standards) or continuous communication silence/pulse signal interruption exceeding a preset time constant, the system will immediately record fault code C111013. This logic aims to exclude surge interference during cold starts and ensure that final assessment of line health is conducted only in stable running states.