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) — Seal U

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).

The B2A5913 fault code on the Seal U indicates an open circuit in the driver-side footwell air outlet temperature sensor signal circuit. Severity is high because it can disable driver-side temperature control and may affect compressor or thermal management operation. Common causes include a failed NTC sensor or poor contact at the right domain controller G86(G) connector pins. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Open circuit in the NTC element inside the sensor body: Long-term thermal cycling causes the thermistor to age and fracture, or internal solder joints become cold or detached.
  • 2Abnormal pins in the right domain controller G86(G) connector: Pin 27 (signal) or pin 28 (ground) is 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 operations easily compromise it).
  • 3Physical damage to the wiring harness: Dashboard removal and installation, carpet water ingress, or loose harness retaining clips can chafe or break the signal wire, especially at the HVAC assembly to body harness connection.
  • 4Loose sensor installation: Temperature sensor not fully clipped into the evaporator housing air outlet, placing tension on the connector and causing poor contact.
  • 5Controller internal sampling circuit fault: Open circuit in the 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 and 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 removal tool to straighten any 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 ambient temperature, the standard resistance is 2kΩ-10kΩ (refer to the specific vehicle manual). Heat the sensor tip with a hot air gun and confirm 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 <1Ω). Test 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: Upon confirming a faulty sensor, replace it with a genuine temperature sensor (Part No.: XXX-XXXXX). During installation, apply thermal grease for proper contact with the air duct wall and fully seat the keyed connector.
  • 6
    System calibration: Restore the power supply and clear fault codes. On some models, perform the 'Air Conditioning Initialization Learning' or 'Temperature Sensor Calibration' procedure (via the diagnostic tool special functions menu).
  • 7
    Function check: Start the vehicle and set the A/C to AUTO mode. Monitor the data stream to verify the driver's footwell temperature changes normally according to 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 Seal U Fault Codes
B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.