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 8

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 8
  • 1Open circuit in the sensor body internal NTC element: Long-term thermal cycling causes the thermistor to age and fracture, or internal solder joints are cold or detached.
  • 2Abnormal pins in right domain controller G86(G) connector: Pin 27 (signal) or pin 28 (ground) bent, backed out, or spread, causing excessive contact resistance or a complete open circuit (this connector sits below the right front A-pillar; previous repair work easily damages it).
  • 3Wiring harness physical damage: Dashboard removal and installation, carpet water ingress, or loose harness retaining clips cause signal wire chafing or breakage, especially at the connection between the HVAC assembly and the body harness.
  • 4Loose sensor installation: Temperature sensor not fully clipped into the evaporator housing air outlet, placing stress on the connector and causing poor contact.
  • 5Internal controller sampling circuit fault: Right domain controller internal signal sampling pull-down resistor open circuit or damaged ADC port (relatively rare)
What To Do
  • 1
    Diagnostic tool data stream verification: Connect the VDS or Launch diagnostic tool, enter the air conditioning system, and read the 'driver footwell temperature' data stream. Verify if it displays -40°C, 255°C, or a fixed abnormal value.
  • 2
    Connector physical inspection: Disconnect the battery negative terminal, remove the right front lower guard panel, and check the condition of pins 27 (signal) and 28 (ground) on the right domain controller G86(G) connector. Use the dedicated terminal removal tool to straighten bent pins, and check for pin push-back 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 ambient temperature, standard resistance is 2 kΩ-10 kΩ (refer to the specific vehicle manual). Heat the sensor tip with a hot air gun and verify the resistance decreases smoothly as temperature increases (NTC characteristic).
  • 4
    Harness continuity and insulation test: Measure harness resistance between the sensor connector and terminal G86-27 (should be <1 Ω). Measure the signal wire for a short to ground or +B (should be >10 MΩ). Inspect the harness specifically at the dashboard frame crimp points and firewall pass-through.
  • 5
    Component replacement and reset: If testing confirms a faulty sensor, replace it with a genuine temperature sensor (Part No.: XXX-XXXXX). During installation, apply thermal silicone grease to ensure good contact with the air duct wall, and fully seat the keyed connector.
  • 6
    System calibration: Restore power and clear fault codes. On some models, perform the 'A/C initialization learning' or 'temperature sensor calibration' procedure (via the diagnostic tool special function menu).
  • 7
    Function check: Start the vehicle, turn on A/C AUTO mode, and monitor the data stream to verify the driver's footwell outlet temperature changes normally when adjusting the set temperature. Confirm the fault code does not recur.
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 8 Fault Codes
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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
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.