B2E8100 4G Sub-Antenna Fault Technical Specification Document

### Fault Severity Definition

DTC B2E8100 explicitly indicates a communication link anomaly or physical functionality failure between the key component in the vehicle's communication system—the 4G Sub-Antenna—and its control terminal. In the vehicle's overall electronic electrical architecture, the center display host, as the core control unit (ECU) of the Information and Infotainment System (IVI), is responsible for processing signal input from the 4G data communication module and protocol conversion. When the fault detection unit detects this DTC, it indicates that the system failed to receive effective feedback signals from the 4G Sub-Antenna within the expected timeframe, or that the radio frequency function at the antenna end does not meet the vehicle network connection requirements. This fault belongs to the bottom-level hardware diagnosis category of the vehicle network communication layer and is directly related to the physical integrity of onboard network (V2X), online navigation, and remote control functions.

### Common Fault Symptoms

Based on system log records and user feedback data, when the B2E8100 fault code is lit, the specific manifestations observable by the vehicle owner mainly focus on functional loss in the onboard information interaction module. Specific symptoms include but are not limited to:

• Partial functionality failure of the center display host (e.g., inability to create Wi-Fi hotspot, interruption of map online search function);
• Missing 4G signal bars or abnormal network status prompts displayed on the instrument panel or vehicle interface;
• Response delay or connection timeout of the voice recognition system due to hindered data return;
• System stability issues such as program lagging, black screen restart, etc., appearing on the center display under specific driving conditions.

### Core Fault Cause Analysis

According to diagnostic database records, the trigger logic for this fault code is mainly attributed to hardware or connection state anomalies in the following three dimensions:

• Lines and Connectors (Physical Connection Layer): Involve the vehicle wiring harness connecting the center display host and the 4G Sub-Antenna. Faults may stem from loose connections on connector terminals, pin withdrawal corrosion, wire harness insulation layer damage causing short circuits to ground or signal line open circuits. Such impedance changes in physical connections will directly block the control unit from reading the status of the antenna port.

• Hardware Components (Actuator Layer): Internal circuit faults within the 4G Sub-Antenna itself, including damaged RF front-end modules, poor feeder connections, or physical damage to the antenna path. As a physical terminal for signal transmission and reception, its failure leads to the host unable to complete antenna handshake protocol verification.

• Controller (Logic Operation Layer): Hardware aging or logic judgment anomalies in the communication control unit (T-Box integrated module) inside the center display host. For example, failure of the internal antenna driver chip means that even if the physical antenna is normal, the host cannot parse the pulse signals or status data fed back by the antenna.

### Technical Monitoring and Trigger Logic

The On-Board Diagnostic System (OBDII/UDS) adopts a dynamic monitoring mechanism for this fault code, with specific judgment logic as follows:

• Monitoring Target: The system continuously monitors the communication link status between the center display host and the 4G Sub-Antenna, focusing on signal integrity, communication handshake response time, and port electrical status. The core focus is on whether the control unit can normally read the identity verification identifier (ID) and connection confirmation code returned by the antenna module.

• Trigger Conditions: This fault judgment is valid only when the ignition switch is ON or the vehicle is running; at this time, the system enters active communication monitoring mode. After the vehicle network wakes up, the diagnostic program will continuously detect the connectivity of the antenna port within a preset window period; if effective antenna response signals are not received within the specified time, an abnormal state is determined.

• Threshold Judgment: The system triggers fault recording when detecting that the antenna connection status signal (e.g., open or short circuit identifier) does not match the normal baseline state during continuous monitoring. Once this state is confirmed and cannot be reset via system restart, the diagnostic tool writes DTC B2E8100 and stores historical fault frame data for subsequent analysis.