U111986 - U111986 RCR_R Signal Invalid

U111986 RCR_R Signal Invalid

Fault Depth Definition

This DTC U111986 points to a critical communication link anomaly in the vehicle domain control network, specifically manifested as RCR_R signal invalid. In automotive electronics architecture, this signal carries critical operational data from the right-rear millimeter-wave radar system back to the main controller. When the system judges it as "invalid", it means the ECU has failed to receive physical location, rotational speed, or status confirmation information conforming to protocol specifications. This DTC is directly associated with the data closed loop of the Adaptive Cruise Control System (ACC). If the RCR_R signal is continuously lost or validation fails, the system cannot establish a complete perception feedback loop, leading to degradation of advanced driver assistance functions to ensure driving safety. This definition strictly follows the logic determination in the original DTC data: that the input signal received from the right-rear millimeter-wave radar system does not meet validity thresholds.

Common Fault Symptoms

Regarding the triggering situation for this DTC, the system will present the following perceptible driving feedback on the diagnostic tool or dashboard:

• Adaptive Cruise System Function Failure: The ACC control unit cannot maintain the set following distance or vehicle speed; the system may automatically exit operation.
• Right-Rear Radar Monitoring Missing: Environmental perception data to the right rear of the vehicle cannot be uploaded to the central controller, which may limit blind spot detection functionality.
• Dashboard Warning Information: The driver may observe ADAS-related icons illuminated or fault indicator lights flashing on the dashboard.
• Function Restriction Prompts: The vehicle's human-machine interface may display prompts indicating that related auxiliary functions are temporarily unavailable to guide drivers to pay attention to driving safety.

Core Fault Cause Analysis

According to the diagnostic logic of U111986 RCR_R signal invalid, the main reasons causing the control unit to fail to confirm signal validity can be classified into the following three technical dimensions:

• Hardware Component Failure: Electronic component damage within the right-rear millimeter-wave radar system itself, loss of sensor calibration data, or anomalies in core processing chips directly result in the inability to generate compliant RCR_R original pulse signals.
• Wiring and Connector Connections: The harness connecting the controller and the right-rear millimeter-wave radar has physical open circuits, short circuits, or high impedance; relevant connectors may suffer from poor contact, bent pins, or oxidation/corrosion, causing signal attenuation during transmission to an unrecognizable state.
• Controller Logic Computation Abnormality: Software algorithms within the vehicle main control unit responsible for parsing radar signals fail, or insufficient hardware resources prevent normal validation of input voltage and signal integrity, erroneously judging valid signals as invalid states.

Technical Monitoring & Trigger Logic

The determination of this DTC strictly follows preset diagnostic monitoring parameters and operating conditions. Specific triggering mechanisms are as follows:

• Monitoring Target: Core monitoring of real-time validity of the RCR_R signal, stability of control unit supply voltage, and vehicle network communication health.
• Numerical Range Restrictions: Under the premise that the system judges signal validity, it requires the input voltage during controller operation to remain stable within the range of $9V$~$16V$. If voltage exceeds this threshold, the system will pause relevant logic operations to prevent false positives.
• Specific Trigger Conditions: The system only records and confirms this DTC when ALL of the following conditions are met:
  • Vehicle complete power-on initialization within $3s$;
  • Public CAN bus network has not entered busoff (stop working) state, ensuring physical connectivity of communication channel;
  • Factory mode is turned off, excluding interference under calibration environment;
  • No power-down notification received from the Body Control Module (BCM), confirming main power supply state;
  • When controller detects a service layer DTC signal appearing and persists for $3s$, system finally locks this DTC.

The above monitoring logic ensures that U111986 fault code is only established when the vehicle is running normally and satisfies specific voltage and communication protocol requirements, avoiding misdiagnosis caused by instantaneous signal fluctuations or during vehicle sleep periods.