B2A5B13 - B2A5B13 Passenger Foot Vent Outlet Temp Sensor Open Circuit

B2A5B13 Fault Severity Definition

This DTC (B2A5B13) corresponds to the automotive air conditioning control unit (CCU) monitoring of the electrical circuit status of the passenger side footwell outlet temperature sensor. In the thermal management system, this sensor is responsible for collecting real-time ambient environment data in the passenger side footwell outlet area as a key input signal for closed-loop control, directly participating in the calculation of AC system actuator execution strategies. When the system monitors an "open circuit" (Open Circuit) status on this sensor circuit, it implies physical connection interruption or abnormally high impedance, causing the CCU to fail to obtain effective analog signal voltage, thereby compromising the integrity of the temperature feedback loop. This fault determination logic belongs to hardware layer health check in the vehicle intelligent diagnostic system, aimed at preventing HVAC actuators from undergoing unswitched operation mode changes due to control unit misinterpretation of environmental parameters.

Common Fault Symptoms

When DTC B2A5B13 is recorded in the system, car owners may observe the following phenomena in driving experience or instrument feedback:

• Partial AC System Function Failure: The system automatically enters fail-safe mode or default strategy status, leading to inability to adjust outlet air temperature.
• Footwell Outlet Temperature Control Malfunction: Drivers and passengers may feel that cooling or heating effects of the passenger side footwell area deviate significantly from set values.
• Instrument Warning Information: HVAC related fault lights may turn on or text prompts may appear in vehicle information display systems (e.g., "HVAC System Check Required").

Core Fault Cause Analysis

Based on system architecture diagnostic logic, the generation of this DTC can be attributed to hardware or software anomalies in the following three dimensions:

1. Hardware Component Failure: Internal circuit damage inside the right front footwell temperature sensor, causing the sensor to fail to output normal ratio signals, identified as open circuit by the controller.
2. Wiring and Connector Failures: Harness connecting sensor and control unit exists breakage, wear, or relevant connector terminal poor contact, pin retreat, creating high impedance connection.
3. Controller Logic Anomaly: A/D conversion module or processing circuit inside right domain controller responsible for reading analog signal voltage has failure, causing misjudgment of normal voltage signals.

Technical Monitoring and Trigger Logic

CCU determines such faults via continuous current voltage monitoring logic, with specific technical determination criteria as follows:

• Monitoring Target: Integrity of ground voltage signal on sensor output loop.
• Voltage Threshold Determination: CCU detects sensor output voltage higher than $4.95V$. Usually, open circuit status leads to line floating or shorting to power, where voltage reading deviates significantly from normal operating range. This value threshold is the critical limit for triggering fault record, system will consider voltage fluctuations exceeding this upper limit as signal abnormality.
• Operating Condition Monitoring Mode: Diagnostic logic monitors in real-time only when ignition switch is in IGN ON/OK state, ensuring control unit is in power on status.
• Fault Enable Mechanism: When satisfying above electrical characteristic conditions and DTC setting enabled (DTC Setting Enabled), system will record this temporary or permanent fault code in storage area, and prohibit related functions from entering normal adjustment mode.