C1BA024 - C1BA024 Main_Angle_Aux_Angle Signal Level Continuously High

C1BA024 Fault Diagnostic Technical Document

Fault Depth Definition

C1BA024 is a specific fault diagnostic code in the Electric Power Steering (EPS) system, with its core definition being "Main/Aux Angle Signal Level Continuously High". In the electronic control architecture, this DTC involves the integrity of the steering motor position feedback loop. Main angle sensors and Aux angle sensors typically use Hall Effect or Rotary Transformer technology to provide real-time feedback on physical motor position and rotation speed data. When the controller monitors that input ports remain in a Logic High state instead of generating expected dynamic changing signals with motor rotation, this fault is determined. This state indicates that during motor drive operation, the system receiver fails to acquire effective pulses or analog feedback, preventing the Steering Assist Control Unit from accurately calculating assist torque and steering wheel self-centering requirements.

Common Fault Symptoms

Based on the characteristic of continuous high-level signal, vehicles at the driver end may exhibit the following perceptible phenomena:

• Instrument Panel Alarm: EPS system indicator light (typically displaying a battery shape or steering wheel with exclamation mark icon) illuminates.
• Steering Feel Abnormal: Under specific conditions, the steering wheel may feel heavy mechanically, or exhibit slight vibration at standstill (depending on controller strategy).
• Function Limitation: The Steering Assist System may enter a protection mode (Limp Home Mode), leading to restricted assist output or only functioning in partial speed ranges.
• Driving Stability Risk: Due to loss of position feedback, Electronic Stability Control Systems (ESP/ESC) may fail to accurately perceive front wheel angles, affecting vehicle dynamic control accuracy.

Core Fault Cause Analysis

According to existing original data, the root causes of C1BA024 can be classified into three technical dimensions for troubleshooting and understanding:

• Angle Sensor Wiring Fault Refers to physical connection harness issues between steering motor position sensors and control units (ECU/Controller). This includes signal lines shorting to power positive, shorting to ground causing inability to form low-level changes, or high line impedance pulling voltage above high-level threshold. Such physical damage directly causes controller input ports to read incorrect "High" state values.
• EPS Controller Internal Fault Refers to hardware failure of signal acquisition circuits or logic processing chips within the steering control unit. For example, A/D conversion modules responsible for receiving angle signals damaged, abnormal pull-up resistors, or Input Buffer breakdown, causing controller unable to sample correctly upon receiving any external signal, defaulting to lock at high-level state.
• Sensor Internal Abnormality Although original data did not explicitly list it, combined with "Wiring Fault" and "Controller Fault", if the sensor itself experiences open circuit or internal circuit shorted to VCC terminal, it can also trigger this DTC, requiring inclusion in hardware component dimension consideration.

Technical Monitoring and Trigger Logic

The control unit's determination of this fault follows the following strict monitoring process and technical logic:

• Monitoring Target: Core is on real-time polling of input signal voltage status for Main/Aux angle sensors. System not only monitors signal existence but verifies if signals present normal frequency modulation or voltage fluctuation characteristics with motor rotor rotation.
• Trigger Thresholds and Conditions:
• Logic Level Determination: When input pin voltage remains above Logic High level reference value ($V_{High}$) continuously, system determines abnormality. Original data explicitly states "Level Continuously High", meaning signal did not switch as expected.
• Specific Condition Dependency: This fault usually triggers after EPS system power-up self-check or passing into steering drive motor operation stage. Monitoring window covers vehicle stationary (idle) and dynamic steering (low speed large angle/high speed small angle) full process. If during this period signals remain unchanged and stay at high level state, timer timeout or counter reaches preset threshold, Fault Code C1BA024 is lit and stored in memory.
• Data Processing Logic: Controller attempts to exclude instantaneous interference via software strategies (such as redundant comparison of Main/Aux angle data). Once data shows "Continuously High" across consecutive multiple sampling periods and cannot be resolved into effective position information, it confirms permanent hardware or wiring fault, then executes corresponding DTC storage and driving intervention logic.