C100203 - C100203 Left Rear TPMS Module RF Communication Fault

Fault Depth Definition

C100203 Diagnostic Trouble Code (DTC) indicates a "Left Rear Tire Pressure Monitoring Module RF Communication Fault" within the vehicle's Vehicle Electronic-Electrical Architecture. This code represents an abnormal interruption or logic error in the Radio Frequency (RF) communication link responsible for managing the left-rear tire pressure monitoring sensor (TPMS Sensor) within the vehicle network system.

Under a typical Domain Controller architecture, tire pressure data from the left-rear tire must interact in real-time with the main control unit via high-frequency radio waves. The triggering of this DTC means the control unit cannot correctly receive, parse, or maintain RF feedback signals between itself and the left-rear TPMS module. This state directly disrupts the "Sensor - Gateway - Controller" data stream within the system loop, preventing the control end from calibrating tire pressure values using physical position information (such as the physical wheel position corresponding to wheel speed pulses). Consequently, this causes partial failure of relevant functions related to chassis safety and vehicle dynamic perception on the Left Domain Controller.

Common Fault Symptoms

When C100203 is triggered, the vehicle's diagnostic system and user interface will exhibit the following feedback characteristics:

• Dashboard Warning: The TPMS (Tire Pressure Monitoring System) warning light typically illuminates on the driver's instrument panel, or display text such as "Left Rear Tire Pressure Not Set/Unable to Monitor" appears.
• Function Module Downgrade: Auxiliary functions relying on this communication link in the Left Domain Controller are activated to protection mode, and some driving information display areas may show data blanks or freezing phenomena.
• System Status Abnormality: The fault code will be recorded and stored during vehicle self-check (OBD). When the vehicle enters maintenance mode or specific diagnostic modes, readings from relevant wheel position sensors will be missing.

Core Fault Cause Analysis

For the diagnosis of C100203, potential failure sources need to be localized from three dimensions: hardware components, physical connections, and controller logic:

• Harness or Connector Fault:
  • The physical wiring harness (Harness) between the Left-Rear Domain Control Unit and the TPMS module exists open circuits, short circuits, or ground/power supply short circuit phenomena.
  • High-frequency vibration during vehicle movement may cause loose contacts, loosening, or oxidation/corrosion on the RF antenna feedline or connector pins, resulting in abnormal signal transmission impedance.
• RF Controller Fault:
  • The wireless RF transceiver (Transceiver) hardware inside the left-rear TPMS module fails, unable to generate effective carrier signals.
  • The antenna unit of the monitoring module is physically damaged or shielded by metal (e.g., interference from added parts), causing the RF communication signal-to-noise ratio to fall below the threshold.
• Left Domain Controller Fault:
  • The decoding circuit inside the control unit for processing RF signals has hardware anomalies and cannot correctly parse received RF data packets.
  • Communication protocol stack or software state machine logic errors in the control unit fail to correctly handle signal handshake requests (Handshake Request), leading to false reports of communication loss.

Technical Monitoring and Trigger Logic

The system's fault determination relies on real-time dynamic monitoring of wireless RF communication quality. Its technical logic is as follows:

• Monitoring Target:
  • The control unit continuously monitors the RF carrier signal strength coming from the left-rear tire pressure sensor.
  • The monitoring system checks the checksum of received data packets and the integrity of modulated data.
• Judgment Threshold and Range:
  • The system evaluates the presence of RF signals within a preset communication time window. If the signal voltage or logic level is below the minimum threshold required to maintain normal communication, or if communication timeout exceeds the allowable time tolerance, it is judged as a fault.
  • Specific numerical ranges depend on the RF sensitivity standards (e.g., Received Signal Strength Indication RSSI) set in the vehicle's underlying control strategies.
• Specific Condition Trigger:
  • This fault is typically recorded during system initialization or dynamic monitoring during driving.
  • When the vehicle is in the Ignition On state and the TPMS system enters a self-check or activation cycle, if the expected left-rear wheel RF response signal cannot be obtained, the control unit will judge "RF Communication Fault" and illuminate the corresponding instrument indicator.