In-depth Analysis of Passenger Seat NTC Open Circuit Fault B18F613

In-Depth Fault Definition

The fault code B18F613 in vehicle electronic architecture is defined as "Passenger Seat NTC Open Circuit". This diagnostic information is generated by the Right Domain Controller to monitor the integrity of the temperature feedback loop in the passenger seat heating system. As a core sensing component, the NTC (Negative Temperature Coefficient thermistor) function is to collect the physical temperature state of the seat surface in real time and provide precise resistance signals to the control unit to adjust heating power. When the monitoring circuit detects that the signal line of the NTC thermistor is in an open-circuit state, it means the temperature feedback link is interrupted. The control unit will not be able to know the current seat surface temperature, which may trigger an overheating protection mechanism or disable the heating function to ensure system safety and comply with design specifications. This definition clarifies that the key component involved in the fault code is the signal interaction logic between the seat heating actuator and the Right Domain Controller.

Common Fault Symptoms

Based on the underlying logic of fault code B18F613, owners may observe the following specific manifestations during driving:

• Passenger Seat Heating Function Failure: When users attempt to activate the passenger seat heating setting, the heating element does not produce heat, and the seat remains at room temperature.
• Instrument Panel Warning Light Abnormality: Some models will display "Seat Heating Failure" or related warning icons on the instrument cluster or vehicle display interface.
• No Response for Heating Indicator Light: After manipulating the control switch, the corresponding temperature indicator ring or LED backlight cannot be illuminated, indicating that the control system has not executed the instruction.

Core Fault Cause Analysis

According to the fault mechanism and electrical architecture, the root causes leading to passenger seat NTC open circuit can be summarized into the following three technical dimensions:

• Hardware Component Failure: The NTC thermistor inside the passenger seat assembly itself undergoes open-circuit damage, resulting in an infinite resistance value state, unable to normally output analog voltage signals.
• Wiring and Connector Faults: The harness connecting the Right Domain Controller and the passenger seat has broken wires, damaged insulation layers or wear; connectors on the seat side or vehicle body side become loose due to vibration, pin backing out or oxidation, leading to loss of physical conductivity.
• Controller Internal Logic Operation: The signal acquisition circuit inside the Right Domain Controller shows anomalies, unable to correctly identify external input voltage, misjudging as open-circuit signals (although probability is low, it needs to be included in the diagnostic sequence).

Technical Monitoring and Trigger Logic

The determination of this fault code is based on strict dynamic monitoring algorithms and electrical parameter thresholds. The system only stores DTC when detecting abnormal values under specific working conditions. Specific monitoring logic as follows:

1. Monitoring Target: System continuously collects signal features at both ends of the NTC thermistor, core criterion is NTC thermistor resistance value infinity.
2. Voltage Threshold Range: During determination, control unit confirms supply voltage is stable within effective working interval $9V$~$16V$, excluding false alarms caused by whole vehicle power being too low or high.
3. Trigger Condition: Fault activated and recorded only under following compound conditions:
   • Vehicle in ON state (ignition switch on);
   • Right Domain Controller has received valid passenger seat heating signal issued from user side.

Only when above voltage range, ignition status and instruction validity are met simultaneously, and sensor feedback resistance value exceeds physical upper limit allowed by closed-loop logic, system establishes B18F613 fault code.