U10B819 - U10B819 MRR Checksum Error

Detailed Fault Definition

Fault Code U10B819 indicates "MRR Checksum Error" in the vehicle network communication system. MRR (Mid-Range Radar) serves as a core sensing component of the Advanced Driver Assistance System (ADAS), responsible for sending target distance and relative speed data to the domain control unit. This fault code indicates that the data integrity validation mechanism (such as Checksum or Counter validation) failed when the control unit received radar messages. This usually means damage to the data frame structure in the communication link or logic anomalies in the signal source, causing the control unit to distrust the currently received radar sensing information and trigger network communication class fault storage.

Common Fault Symptoms

When MRR Checksum Error is activated, the vehicle's driver assistance system usually enters a degraded or unavailable state, and the owner may perceive the following phenomena:

• Dashboard displays warnings that the driver assistance system (such as Adaptive Cruise Control, Automatic Emergency Braking) is unavailable or restricted.
• Radar-related function icons in the display appear gray or with fault indicators.
• The vehicle cannot activate dynamic control functions depending on the front-mounted millimeter-wave radar.
• The system may record relevant network communication loss history data.

Core Fault Cause Analysis

Based on the system architecture, potential causes for this fault can be categorized into the following three technical dimensions:

• Hardware Component Dimension: Involves Front-mounted Millimeter-wave Radar Fault or abnormality of power protection components. Internal chip calculation errors within the radar may generate incorrect checksums, while Fuse Failure may lead to unstable radar power supply, subsequently causing signal transmission distortion.
• Wiring/Connector Dimension: Corresponds to Harness or Connector Fault. Physical connection layer impedance changes, signal interference, or poor contact directly damage message integrity on the CAN bus, leading to reception side validation failure.
• Controller Dimension: Involves logic computation units on the receiving end. If communication protocol stack parsing logic within the controller is abnormal, or if message processing times out under specific loads, it may also be misjudged as a checksum error.

Technical Monitoring and Trigger Logic

The system determines whether this fault holds true through specific logic thresholds and operating conditions, with specific monitoring mechanisms as follows:

• Monitoring Target: System monitors the integrity of communication messages sent by the front-mounted millimeter-wave radar in real-time.
• Lost Count Threshold: When any monitored message is continuously lost up to $10$ times, it meets the counting trigger condition.
• Voltage Work Window: Fault determination takes effect only when controller voltage is within the effective operating range of $9V$~$16V$.
• Time Sequence Conditions: System needs to start executing this fault logic monitoring $3s$ after power-on initialization.
• Communication State Constraint: During monitoring, Private CAN Network must not enter Bus-Off state, ensuring basic physical layer normality of communication link.
• Mode State Constraint: Vehicle must be in Factory Mode Off status, i.e., this end-user fault code triggers only under non-production debugging mode.