U024687 - U024687 Lost Communication with MPC

DTC U024687 Lost Communication with MPC

### In-depth Fault Definition

In vehicle control network architecture, diagnostic trouble code U024687 is identified as "Lost Communication with MPC (Multi-Function Video Controller)". This DTC involves data link layer integrity checks within the whole vehicle domain, primarily pointing to communication anomalies between the powertrain or body controller and the MPC node on the CAN bus. As a key execution and control unit, MPC is responsible for processing video streams, multimedia signals, and system instruction transmission. When bidirectional messages between control units fail to complete periodic handshakes according to preset protocols, the system will judge the network link as ineffective. This fault not only represents physical connection interruption but also implies that the heartbeat monitoring mechanism in control strategies has been activated, indicating that the MPC node cannot respond to main network control requests within agreed time, leading some vehicle electronic systems to enter safe degradation mode and system functions fail.

### Common Fault Symptoms

Due to disconnection of communication link, drivers or passengers may perceive the following abnormal manifestations, these symptoms are usually directly associated with the multimedia and display modules of the infotainment system:

• Instrument or Center Screen Display Anomalies: Multi-function video controller black screen, garbled screen, or unable to light up corresponding information display areas.
• System Function Unresponsive: Attempting to call vehicle multimedia menus, volume control or video input sources, commands cannot be executed or interface refresh fails.
• Warning Lights On: Communication network fault indicator or system failure icon appears on the dashboard, accompanied by storage records of relevant codes.
• Data Transmission Interruption: External video signals or audio stream transmission processed by MPC interrupted, leading to entertainment function temporarily unavailable.

### Core Fault Cause Analysis

For the logical trigger of this DTC, technical qualification can be conducted from three dimensions of hardware power supply, physical link and control unit logic:

• Hardware Component Failure: Fuses responsible for providing stable electricity to communication nodes have blown or aged, causing MPC controller to malfunction due to undervoltage; meanwhile, internal processors or communication chips within the multi-function video controller itself may appear logically damaged.
• Line and Connector Failures: Harness connecting MPC to control main network has broken, worn or loose connection, causing unstable signal voltage transmission; CAN bus connector pins oxidized loose or contact resistance too large, causing data integrity check failure.
• Controller Logic Anomalies: Internal diagnostic module of multi-function video controller does not report its own status correctly, or there are logic operation errors when receiving monitoring messages, causing control unit unable to identify valid communication frames.

### Technical Monitoring and Trigger Logic

Control unit fault judgment algorithm is based on strict real-time monitoring conditions, only recording this DTC when all preset parameters are met simultaneously:

• Voltage Threshold Monitoring: System continuously monitors supply voltage of MPC controller, only making communication validity judgment when voltage stably within effective working range of $9V$~$16V$. If voltage out of range, communication abnormality will be ignored to exclude power interference factors.
• Time Window Judgment: Fault trigger occurs after $3s$ following vehicle power-on initialization completion. This time period aims to ensure each node completes cold start self-check and enters normal working state before network interaction stage.
• Communication Frequency Monitoring: For any monitoring message issued by MPC, system detects that loss of this message reaches $10$ times within continuous time window, then judging as permanent link interruption rather than instantaneous packet loss.
• Bus and Mode Status Check: Fault trigger premise is Private CAN Bus has not entered Busoff (Offline) state, and system is running in factory mode off state, to exclude diagnostic tool testing or maintenance mode interference on network topology.