U111987 - U111987 Loss of Communication with RCR_R Module

Fault Definition

U111987 Communication Loss with RCR_R Module is a key diagnostic trouble code (DTC) in the vehicle's active safety system, belonging to communication fault codes (usually starting with U). The essence of this DTC reflects that the data link integrity between the control unit and specific radar node has been compromised. In ADAS (Advanced Driver Assistance Systems) architecture, RCR_R module typically refers to the right rear corner radar controller or related sensor node, responsible for acquiring spatial data at specific physical locations.

This fault code setting means the gateway or main control unit in the vehicle network cannot receive valid monitoring messages from the RCR_R module. This communication interruption directly causes control strategies dependent on sensor data computation to fail execution, subsequently affecting whole vehicle safety logic. In underlying communication protocols (like CAN/LIN), this represents node heartbeat loss or data frame checksum error, belonging to serious system-level anomalies indicating unreliable information interaction links in network topology structure.

Common Fault Symptoms

When U111987 fault code is lit or stored, the vehicle's control logic enters protection mode, specific user-perceivable manifestations include:

• Adaptive Cruise Control Function Disabled: ACC (Adaptive Cruise Control) function will be disabled, relevant dashboard indicators will light up warning, and system cannot automatically adjust vehicle speed to maintain safe distance from preceding vehicle.
• Driving Assistance Function Degradation: Other functions relying on radar sensor fusion may be restricted or turned off, entering basic driving mode.
• Instrument Fault Information Prompt: Users may receive specific text prompts such as "Radar System Fault" or "Communication Abnormality" in the central control display or multimedia system.
• Vehicle Dynamic Control Adjustment: In extreme scenarios depending on this communication data for dynamic stability or steering assist, the system may default to disabling related electronic assist to ensure safety.

Core Fault Cause Analysis

According to diagnostic logic tree, U111987 triggering primarily stems from three dimensions of potential problems:

• Hardware Component Abnormality:
  • Internal circuit damage or main control chip failure within the right rear corner radar module itself, leading to inability to send signals.
  • Front millimeter-wave radar has electrical faults; if system architecture requires multi-node communication verification, its abnormality may also affect judgment of this fault code.
• Wiring and Connector Physical Connection:
  • Harness Fault: Transmission cables connecting RCR_R module and control unit appear broken, short-circuited or ground interference, causing data frames unable to transmit completely.
  • Connector Fault: Connector pins on radar and body harness retract/oxidized or contact resistance too large, causing signal transmission unstable or interruption.
• Controller and Power Logic:
  • Fuse blown or circuit protection enabled, leading to insufficient working voltage or zero supply for RCR_R module, putting module in non-active state (Sleep) unable to communicate.

Technical Monitoring and Trigger Logic

Control unit's judgment on this fault follows strict and multi-dimensional time sequence and electrical condition verification mechanism to ensure misjudgment rate minimized:

• Message Continuity Monitoring:
  • System continuously monitors diagnostic messages from RCR_R module. When detecting any monitoring message consecutively lost 10 times, triggering fault judgment logic. This requires fault persistence rather than instant interference.
• Electrical Environment Threshold Limitation:
  • This monitoring logic is valid only within specific voltage intervals, ensuring judgment made within normal operating voltage range. Specifically: Controller voltage range $9V$~$16V$. If beyond this range, system may judge as power supply abnormality rather than communication fault.
• System Initialization Timing Requirement:
  • To prevent cold start initialization jitter affecting diagnosis, must execute fault monitoring only after 3s following power-on initialization.
• Network Topology State Verification:
  • Diagnosis valid only in specific network states, requiring private CAN not entering busoff status. If total control module's private communication channel already failed (Bus-Off), communication interruption may be main line problem rather than RCR_R module itself problem.
• Production Mode Permission Check:
  • System reads internal state registers to ensure fault code output under factory mode off status, preventing false alarms during development or calibration phases.