U112087 - U112087 Communication Lost with VCU

Fault Depth Definition

Fault code U112087 is defined as loss of communication with the Vehicle Control Unit (VCU). In modern new energy vehicle electronic architectures, the VCU acts as the core control unit, responsible for coordinating the power system, energy management, and vehicle status logic. This fault code indicates that the communication link between the current monitoring node and the VCU has been interrupted, causing the control unit to be unable to acquire key vehicle operation parameters. From a system logic perspective, this means data frame transmission for real-time feedback on motor physical position and rotational speed, torque commands, and high-voltage status fails. The closed-loop feedback loop in the control strategy is cut off, forcing the system to enter its default safe state after communication loss.

Common Fault Symptoms

When fault code U112087 is activated, the vehicle typically exhibits the following perceivable driving experience abnormalities or instrument feedback:

• The dashboard illuminates a Vehicle Control System failure warning light or Communication System abnormality indicator lamp.
• The vehicle fails to complete the high-voltage power-on process, resulting in an inability to drive or start.
• The powertrain enters protection mode, with possible limited power output or limp-home mode activation.
• Subsystems working collaboratively based on VCU signals (such as energy regeneration system, thermal management system) malfunction or stop working.

Core Fault Cause Analysis

Based on system architecture and signal flow direction, the causes of this fault can be categorized into the following three technical dimensions:

• Hardware Component Dimension: Starting Battery Fault. As the whole vehicle low-voltage power source, if the starting battery voltage is abnormal or capacity is insufficient, it may lead to unstable power supply to the VCU or Gateway module, causing them to be unable to maintain normal communication transmission function.
• Wiring/Connector Dimension: Harness and Connector Fault. Involves physical connection issues with communication bus (such as CAN bus), including harness open circuit, short circuit, pin corrosion, or excessive connector contact resistance, leading to signal transmission attenuation or physical link interruption.
• Controller Dimension: Vehicle Control Unit Fault. Refers to hardware damage or software deadlock occurring in the internal microprocessor, communication chip, or logic computation unit of the VCU, causing it to fail to periodically generate and send messages according to protocol stack requirements.

Technical Monitoring and Trigger Logic

The system performs real-time scanning of the communication bus status via low-level driver programs. The specific monitoring and judgment logic is as follows:

• Monitoring Target: Control unit continuously listens for VCU identity identification messages and heartbeat signals on the communication bus, verifying message IDs and data integrity.
• Trigger Condition: In a Vehicle Power On state, system communication monitoring module activates, entering dynamic monitoring window.
• Judgment Logic: When within a preset time period no VCU message is received, communication timeout counter overflows, system judges communication link lost, and immediately generates fault code U112087 and records freeze frame data.