U024887 - U024887 Communication Fault With SIM Card

U024887 SIM Card Communication Fault: Definition and System Role

U024887 SIM Card Communication Fault belongs to network communication type diagnostic trouble codes (DTC), with its core code identifier marked as "U", representing the "Network" category. This DTC indicates abnormal interruption of a data link between specific control units within the vehicle's central control electronic architecture (such as gateway, infotainment host, or Telematics Control Unit) when attempting to establish or maintain communication with the onboard SIM card communication module. In modern smart connected vehicle systems, the SIM card module is the key physical carrier for IoV services, responsible for carrying handshake verification and data transmission of mobile communication protocols. The occurrence of this DTC means the control unit failed to receive expected signal feedback or protocol response, resulting in an inability to confirm the integrity and timeliness of the SIM card communication link, belonging to logical determination or physical connection anomaly at the network communication level.

Common Fault Symptoms

When the system records this fault code, users may observe the following specific phenomena during driving, primarily reflected in the infotainment system and IoV functions:

• Infotainment Host Partial Function Failure: The onboard multimedia display area may show black screen, stuttering or response latency, and network-dependent functional modules stop working.
• Network Connection Service Interruption: Online map navigation, voice assistant online wake-up, and vehicle remote control services cannot be used.
• System Status Indicator Anomaly: WiFi or SIM card icons on the instrument panel or central display show abnormal states (such as signal loss or disconnected).

Core Fault Cause Analysis

Based on existing data and vehicle electrical architecture principles, this fault is generally attributed to physical or logical problems in the following three dimensions:

1. Hardware Component Level
   • Infotainment Host Failure: Refers to damage to internal circuits, communication chips or motherboard logic of the host as a data terminal processing unit, causing inability to correctly parse SIM card communication instructions.
   • SIM Card Module Itself Abnormality: Although classified as a communication object, its hardware aging or interface mismatch may also fall into the general category of infotainment host system failure.
2. Wiring and Physical Connection Level
   • Harness or Connector Failure: Data cables (CAN/LIN/FlexRay etc. buses) connecting control unit and SIM communication module have open circuit, short circuit or excessive contact resistance phenomena; meanwhile, relevant connectors (Connector) may have pin corrosion, oxidation or looseness, leading to blocked physical signal transmission.
3. Controller and Logic Computation Level
   • Refers to internal control program (ECU Logic) of control unit having abnormal determination settings for communication timeout time or software algorithm anomalies, misjudging communication delays within normal range as fault states.

Technical Monitoring and Trigger Logic

The setting of this DTC is based on ECU real-time dynamic monitoring of communication link parameters. Internal system control algorithms continuously execute the following monitoring tasks:

• Monitoring Targets

  • Mainly monitors physical signal integrity from SIM card module, data frame response time (Response Time) and communication protocol handshake success rate (Handshake Success Rate).

• Trigger Conditions and Logical Determination

  • Startup Condition Requirement: The specific condition for fault determination is the ignition switch placed in ON position. Only when ignition switch is in running state and system completes power-on self-check, will control unit activate effectiveness monitoring of SIM communication link.
  • Judgment Mechanism: Once system detects no effective ACK response signal within communication cycle, or continuously multiple times monitoring data link integrity check failure (such as $CRC$ check not passing), and duration exceeds preset threshold, system immediately records DTC U024887. This process aims to ensure critical network functions after power-on are available.