U111983 RCR_R Checksum Error - Fault Code Technical Documentation

Fault Depth Definition

U111983 RCR_R Checksum Error is a critical fault code involving the right-rear millimeter wave radar system in the adaptive cruise control system. The core role of this code lies in describing the signal interaction validation status between the control unit and the right-rear millimeter wave radar system. In the system's real-time data feedback loop, the control unit performs integrity checks on received RCR_R data; when actual monitored values do not match preset standards, the system determines a "Checksum Error". This fault indicates that the controller cannot confirm the reliability of real-time information such as physical component (right-rear millimeter wave radar) position and rotation speed, causing the ACC system's decision logic to fail validation and triggering protection mechanisms.

Common Fault Symptoms

Vehicle owners can observe specific system feedback performance in their driving experience:

• Adaptive Cruise Control Function Disabled: The instrument cluster explicitly shows that the Adaptive Cruise (ACC) function is turned off or unavailable; the system cannot intervene in vehicle speed control.
• Limited Vehicle Power Response: Due to safety policy restrictions, the system may prohibit executing constant speed cruise or following instructions, affecting the normal use of driving assistance functions.
• Instrument Warning Lights On: Relevant warning indicator lights activate on the instrument cluster, notifying the driver of right-rear radar communication or operational status abnormalities.
• Control Command Interruption: The vehicle cannot set target speed or distance keeping function is forcibly disabled.

Core Fault Cause Analysis

Based on technical diagnostic logic, causes leading to U111983 RCR_R Checksum Error can be classified and analyzed from the following three dimensions:

• Hardware Component Abnormality: Internal hardware of the right-rear millimeter wave radar system (e.g., sensors, signal processors) experiences physical failure or performance degradation, causing transmitted data to fail control unit validation algorithms.
• Wiring/Connector Connection Issues: Wiring harnesses connecting the controller and right-rear millimeter wave radar system have open circuits or shorts, or connectors have poor pin contact, causing signal transmission integrity loss.
• Controller Logic Calculation Error: The control unit's internal processing logic for RCR_R data deviates, or misjudgment occurs in parsing hardware feedback signals, generating an error code at the data validation level even with normal physical connections.

Technical Monitoring and Trigger Logic

The system determines fault occurrence based on strict electrical parameters and timing logic; specific trigger conditions and monitoring thresholds are as follows:

• Power Voltage Range Monitoring: Controller must be in a stable operating voltage range, specifically $9V$~$16V$. Outside this voltage range, the system will suspend relevant validation functions.
• Power-Up Initialization Timing: Fault detection logic only becomes effective 3s after vehicle power-up initialization is complete to ensure system self-check status reset.
• Continuous Failure Judgment Frequency: Fault code triggering depends on monitoring results; when any monitoring validation fails consecutively cumulatively reaching 3 times, the system confirms current faults exist.
• Bus Communication State Requirements: During diagnosis, Universal CAN Bus (Master CAN) must remain active; strictly prohibited from entering busoff state to ensure normal upload and interaction of fault information.
• System Operating Mode Restrictions: Precondition for triggering this fault is that the vehicle is not in production debugging state, meaning factory mode must be turned off to exclude development stage environmental interference.
• External Communication Sync Conditions: System needs to ensure no power-down notification received from Body Control Module (BCM), and after service detection record DTC requires 3s specific delay processing before finally solidifying the fault code.