U110187 - U110187 Loss of Communication with Combined Switch

Deep Definition of DTC U110187 Fault

DTC (Diagnostic Trouble Code) U110187 belongs to the general protocol communication fault category, indicating an interruption or anomaly in the data link between the vehicle's central control unit and the Combination Switch. Within the architecture of the Adaptive Cruise Control (ACC) system, this Combination Switch serves as a critical human-machine interaction node, responsible for real-time acquisition of driver speed setting commands, cruise activation status, and distance adjustment signals. This fault code signifies that the control unit cannot receive effective monitoring messages from the Combination Switch, resulting in a breakage of the Feedback Loop. The system-level diagnostic logic determines this as "Communication Loss", aiming to eliminate the risk of control information loss caused by poor hardware connection or network topology anomalies, ensuring data synchronicity between the vehicle power management module and body control nodes.

Common Fault Symptoms

The manifestations of this fault at the driver end mainly involve limitations in auxiliary driving functions and changes in dashboard feedback signals. Specific symptoms include:

• Partial Failure of Adaptive Cruise System Functions: The ACC system enters a degraded operation mode and cannot execute automatic acceleration/deceleration or automatic following logic.
• Dashboard Warning Lights Illuminated: Fault indicator lights related to the Combination Switch or ACC system status icons display abnormal warning information on the dashboard.
• No Response to Control Inputs: Operations performed by the driver using the cruise control buttons on the steering wheel (such as setting speed, resume/cancel) may temporarily lose expected functionality.
• Restricted Speed Holding Mode: The system may only allow operation in a fixed mode and cannot enter a fully automated dynamic driving mode.

Core Fault Cause Analysis

According to feedback from original data, the root cause of the fault can be located from three dimensions: hardware components, physical connections, and control logic:

• Hardware Component Failure:

  • Combination Switch Internal Failure: The switch body electronic unit is damaged or sensors fail, resulting in an inability to send communication messages.
  • Forward Millimeter Wave Radar Failure: In some integrated architectures, the radar module as one of the system communication nodes, its own anomaly may concurrently trigger link protection mechanisms.
  • Power Supply Component Abnormality: Fuse failure is a common power supply source issue leading to communication interruption, potentially causing node voltage below working thresholds.

• Line and Connector Failure:

  • Harness Physical Damage: The CAN bus harness between the control unit and Combination Switch experiences open circuits, short circuits, or electromagnetic interference attenuation.
  • Connector Poor Contact: Internal terminals inside various electrical interfaces (Connector) are loose, oxidized, or pins drop out, causing physical signal transmission interruption.

• Controller Logic Anomaly:

  • The communication monitoring module inside the main control unit failed to correctly parse signal frames from the Combination Switch, belonging to a logical judgment fault at the control level.

Technical Monitoring and Trigger Logic

System diagnostic algorithms determine DTC U110187 based on strict voltage and environmental condition thresholds. Specific monitoring parameters are as follows:

• Controller Operating Voltage Monitoring The system activates communication monitoring functions only when the power system voltage is within an effective operating range, preventing false alarms due to low voltage. Trigger conditions require: $9V$~$16V$. If voltage exceeds this range (e.g., during engine start or battery depletion), the system will pause fault recording.

• Initialization and Status Waiting Fault determination does not occur immediately but goes through a necessary system self-check cycle. The specific process is as follows:

  • After power-on initialization, wait for $3s$.
  • Continue monitoring when the General CAN bus has not entered Busoff protection status.
  • Complete determination before receiving the power-down notice from the Body Control Module (BCM) to prevent communication interruption during vehicle power-off from being misread.

• Message Loss and Confirmation Threshold The core criterion for fault is the continuity of the message stream. When the system detects that the frequency of a certain monitoring message is lower than the expected level, it must be accumulated continuously. Specific setting conditions are: any single monitoring message lost continuously$10$ times. Only when this event occurs under all above voltage and mode conditions (factory mode off, no BCM notification received, etc.), and service detects DTC and continues for $3s$ afterwards, the final U110187 fault code is generated.