AU
B2A5913

This DTC indicates an open circuit in the signal circuit of the driver-side footwell air outlet temperature sensor (NTC negative temperature coefficient thermistor) — Atto 3

Thermal Management System

This DTC indicates an open circuit in the signal circuit of the driver-side footwell air outlet temperature sensor (NTC negative temperature coefficient thermistor).

In BYD dual-zone/multi-zone automatic air conditioning systems, this sensor provides real-time footwell air outlet temperature feedback to the air conditioning controller (integrated into the right domain controller) for closed-loop temperature control.

An internal open circuit in the sensor, an open circuit in the wiring harness, or poor connector contact causes the controller to detect a signal voltage outside the valid range (typically reading -40°C or a fixed high voltage) and trigger this DTC.

This fault disables driver-side temperature control and may force the compressor into protection mode.

In extreme cases, it disrupts the coordinated operation of the battery thermal management system (on models with coupled air conditioning and battery cooling circuits).

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Open circuit in the sensor body internal NTC element: Long-term thermal cycling causes the thermistor to age and fracture, or results in dry or detached internal solder joints.
  • 2Right domain controller G86(G) connector pin abnormality: Pin 27 (signal) or pin 28 (ground) is bent, backed out, or enlarged, causing excessive contact resistance or a complete open circuit (connector sits below the right front A-pillar; previous repair work easily damages it).
  • 3Wiring harness physical damage: Dashboard removal and installation, water-soaked carpets, or loose harness retaining clips can chafe or break the signal wire, especially at the interface between the HVAC assembly and the body wiring harness.
  • 4Loose sensor installation: Temperature sensor not fully clipped into the evaporator housing air outlet, putting tension on the connector and causing poor contact.
  • 5Controller internal sampling circuit fault: Open circuit in right domain controller internal signal sampling pull-down resistor, or damaged ADC port (relatively rare).
What To Do
  • 1
    Diagnostic tool data stream verification: Connect the VDS or Launch diagnostic tool, access the air conditioning system, and read the 'driver footwell temperature' data stream. Verify if it displays an abnormal value of -40°C, 255°C, or a fixed, unchanging value.
  • 2
    Connector physical inspection: Disconnect the battery negative terminal. Remove the right front lower guard panel. Check the condition of pins 27 (signal) and 28 (ground) on the right domain controller G86(G) connector. Use the dedicated terminal release tool to straighten bent pins. Check for pin recession and terminal oxidation.
  • 3
    Sensor resistance measurement: Remove the driver footwell air outlet temperature sensor (located at the bottom of the HVAC assembly) and measure the resistance using a multimeter. At 25°C, the standard resistance is 2kΩ-10kΩ (refer to the specific vehicle manual). Heat the sensor tip with a hot air gun and verify the resistance decreases smoothly as the temperature increases (NTC characteristic).
  • 4
    Harness continuity and insulation test: Measure the harness resistance between the sensor connector and terminal G86-27 (should be <1Ω). Check the signal wire for short circuits to ground and +B (should be >10MΩ). Carefully inspect the harness at the dashboard frame crimp point and firewall pass-through.
  • 5
    Component replacement and reset: If confirming sensor failure, replace the sensor with an OEM temperature sensor (Part No.: XXX-XXXXX). During installation, apply thermal grease to ensure good contact with the air duct wall and fully insert the keyed connector.
  • 6
    System calibration: Restore power supply and clear fault codes. For some models, perform the 'A/C initialization learning' or 'temperature sensor calibration' procedure (via the diagnostic tool special functions menu).
  • 7
    Function verification: Start the vehicle, set the A/C to AUTO mode, and monitor the data stream to verify the driver footwell temperature changes normally with the set temperature. Confirm the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

Bent pin in G86 connector causing intermittent open circuit

✓
Vehicle came in reporting intermittent AC not cooling. Scanner showed DTCs B2A5913 and B2A5813 both present. Data stream showed driver-side face-level and footwell temperatures stuck at -40°C. Inspection of the right domain controller G86(G) connector revealed pin 27 (temperature sensor signal) bent and inserted into terminal 28, causing poor contact. Prior dashboard repair work caused this improper connector fitting. Reseated pin 27 to the correct position. Data stream returned to normal and the fault resolved.
Original source ↗
BYD DTC AI Analysis

Sensor unit aging caused internal open circuit

✓
A 2018 BYD Qin Pro DM at 85,000 km logged DTC B2A5913 in the climate control system; no warm air from the driver's footwell vent. Measured 5V reference at the sensor connector (normal), but the sensor body showed infinite resistance (open). Disassembled the sensor and found the internal NTC thermistor solder joint cracked from long-term vibration and thermal cycling. Replaced the driver's footwell temperature sensor; resistance returned to 4.8kΩ at 25°C, the fault code cleared and dual-zone climate control accuracy returned to normal.
BYD DTC AI Analysis

Screw pinched dashboard wiring harness, causing open circuit

✓
The vehicle set DTC B2A5913 after dashboard removal and refitting during CarPlay module installation. Inspection found a mounting screw had crushed the wiring harness behind the HVAC assembly. The copper conductor of the temperature sensor signal wire had fractured while the insulation remained intact, creating a hidden break. The fault code appeared intermittently when gently pulling the harness. Replaced the damaged harness section, rerouted the wiring to specification, and added protective corrugated tubing to prevent direct contact between the harness and rigid frame, eliminating the fault.
BYD DTC AI Analysis

Loose sensor connector causing poor contact

✓
2019 Song MAX: AC malfunction after routine servicing. Found the driver's footwell temperature sensor connector not fully locked—relying on terminal friction alone and causing signal dropouts over bumps. The sensor sits at the bottom of the HVAC housing above the accelerator pedal in a tight space; the connector likely worked loose during the previous cabin filter check. Reinserted the plug, confirmed the locking tab clicked into place, and cleared the fault codes. Issue did not recur.
BYD DTC AI Analysis

Right domain controller internal sampling circuit fault

✓
A 2019 Qin EV repeatedly logged DTC B2A5913. Replaced the sensor and wiring harness; the fault persisted. Measured 5V at terminal G86-27 to ground (normal is 0.5-4.5V varying with temperature), indicating an open internal pull-down resistor or damaged ADC port in the controller. Replaced the right Body Domain Controller; the temperature signal returned to normal. This hardware fault is uncommon; consider it only after ruling out wiring and sensor issues.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.