U111886 - U111886 Loss of Communication with MPC Module

Fault Depth Definition

DTC U111886 is defined as a specific communication anomaly indicator in the vehicle control network, indicating handshake failure between the host controller and the MPC module (Multiplex Processor Controller). In Advanced Driver Assistance Systems (ADAS) architecture, this code reflects that the core domain control unit cannot receive valid monitoring messages from the MPC module. Analyzing from the system logic level, this DTC marks an interruption of heartbeat signals in the internal network communication protocol stack, causing the main controller to be unable to confirm the online status and working status of the MPC module. Such communication interruptions usually occur in environments based on private CAN (Priv CAN) bus architecture and belong to critical monitoring points for network diagnostics and redundancy control.

Common Fault Symptoms

When U111886 DTC triggers, the vehicle control system will enter a restricted operation mode or function degradation state according to preset logic, specific phenomena perceptible to the driver include:

• Adaptive Cruise Control System (ACC) Failure: The instrument panel shows the ACC function icon extinguished or accompanied by "Communication Error" prompt, system cannot execute speed holding or following instructions.
• Dashboard Warning Messages: The combination instrument screen or central control screen may pop up specific text warnings about MPC module communication anomalies.
• Power Control Limited: According to MPC's functional weight in the whole vehicle network, motor power output limitation or vehicle dynamic control strategy adjustment may occur.
• System Status Indicator Abnormal: Some models may light up "Service", "Check Engine" or dedicated ADAS system fault lights.

Core Fault Cause Analysis

The root cause of this fault lies in the failure of physical connection or logical interaction between the MPC module and network nodes. Based on diagnostic data, it can be categorized into the following three dimensions for technical judgment:

• Hardware Component Power Supply Anomaly: If there is a blown fuse (Fuse) or poor contact in the vehicle circuit system, it will directly cause the MPC module or its communication port to lose working voltage, triggering bus silence.
• Physical Link Connection Fault: Wiring harness aging, loose connectors, or corroded pins will interrupt signal transmission paths. Wiring harness or connector faults are common physical layer failure points, affecting packet integrity transmission and ACK confirmation.
• Network Node Controller Failure: The fault may be related to other key nodes on the communication link, including Multiplex Video Controller (MFVC) and Front mmWave Radar. If these components suffer hardware damage or logical errors, they may interfere with message frame transmission on the Private CAN bus, causing MPC end to detect data stream loss.

Technical Monitoring and Trigger Logic

The diagnostic system follows strict state machine logic to determine and record this DTC. Specific technical trigger conditions and monitoring threshold definitions are as follows:

• Message Loss Threshold: The system continuously monitors monitoring messages (Heartbeat Message) from the MPC module; once detecting any continuous loss of 10 monitoring messages, it is regarded as communication link failure.
• Power Voltage Range Constraint: Fault determination is only valid within specific electrical intervals where the controller operates, with a monitoring range of $9V$~$16V$. Outside this range, the system ignores this communication state to prevent false reports.
• Initialization Time Delay: The fault counter only starts after system power-on initialization completion. Specific trigger conditions need to satisfy the time window requirement of 3s after power-on initialization.
• Safety State Prerequisites:
  • Private CAN not in busoff state: If the communication bus itself is physically disconnected or enters BusOff protection mode, the system judges it as a bus fault rather than a specific module fault. This code is recorded only when Private CAN is working normally.
  • Factory Mode Off: System activates this monitoring logic only when the vehicle is in mass production user mode (i.e., factory mode off), preventing data interference during development test stages.