AU
B2A0F13

This fault code indicates an open circuit in the refrigerant temperature sensor signal circuit at the inlet or outlet of the plate heat exchanger (chiller, battery cooler) — Seal 6 EV

Thermal Management System

This fault code indicates an open circuit in the refrigerant temperature sensor signal circuit at the inlet or outlet of the plate heat exchanger (chiller, battery cooler).

The sensor is an NTC thermistor that monitors the temperature of the refrigerant exchanging heat with the battery coolant, serving as a key feedback component in the BYD thermal management system.

The ECU monitors this temperature to adjust the electronic expansion valve opening and electric compressor speed, precisely controlling the battery pack temperature.

When the ECU detects the sensor signal voltage continuously exceeding the upper threshold (typically the 5V reference voltage, indicating an open circuit), it sets an open circuit fault.

The thermal management system consequently loses precise control over battery cooling and heating.

This failure may trigger the battery thermal management protection strategy, forcing the vehicle into power limitation mode (limp mode), disabling fast charging, or triggering a high coolant temperature warning.

Extreme cases pose a risk of battery thermal runaway.

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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Internal open circuit in the sensor body: Prolonged exposure to high-temperature, high-pressure refrigerant degrades the plate heat exchanger refrigerant temperature sensor (NTC thermistor). This breaks the internal resistor element, resulting in infinite resistance.
  • 2Wiring harness connector loose or terminal pin backed out: Retaining clip failure or incomplete seating loosens the sensor connector (usually a 2-pin plug) located in the high-temperature, high-vibration area of the front compartment. Repeated connecting and disconnecting causes female terminal pins to back out or spread.
  • 3Physical damage to the wiring harness: Vibration and chafing damage the insulation and cause fatigue fracture of the internal copper wires where the wiring harness section from the engine bay to the chassis passes through the firewall, frame mounting holes, or along the edge of the battery pack; or previous repairs crushed or cut the wiring harness.
  • 4Refrigerant leakage corrosion: An aging sealing ring at the plate heat exchanger connection causes a minor refrigerant leak. A mixture of liquid refrigerant and refrigerant oil seeps into the threaded sensor connection, corroding the internal sensor circuit and causing an open circuit.
  • 5Connector oxidation: Poor sensor connector sealing during water exposure or in high-humidity environments causes terminal oxidation or electrolytic corrosion, resulting in a high-resistance open circuit.
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS or a BYD dedicated diagnostic tool to read the DTC freeze frame. Record vehicle speed, battery temperature, ambient temperature, and air conditioning status when the fault occurred. Determine if the fault is historical or current. Check for accompanying thermal management system DTCs (e.g., electronic expansion valve fault or compressor fault).
  • 2
    Visual and wiring inspection: Raise the vehicle. Inspect the sensor at the plate heat exchanger (located in the front compartment, near the battery coolant lines) for deformation or oil leaks. Trace the wiring harness routing and inspect for wear, damaged insulation, or burn marks, focusing on the firewall pass-through and harness retaining clip locations.
  • 3
    Sensor body resistance measurement: Disconnect the sensor connector and use a multimeter to measure the resistance across the sensor terminals. At room temperature (25°C), the standard resistance is typically 2kΩ-10kΩ (refer to the workshop manual for exact specifications). If the reading shows infinity (OL) or the resistance deviates significantly from the standard curve, replace the sensor.
  • 4
    Wiring harness continuity test: Disconnect the connector at the thermal management controller (or relevant module integrated into the air conditioning controller). Measure the wiring harness continuity resistance between the sensor plug and the controller. The resistance must be less than 1 Ω. Measure the resistance to ground; it must be greater than 10 MΩ (to rule out a short to ground). If an open circuit exists, repair or replace the wiring harness.
  • 5
    Connector pin inspection: Inspect the male and female sensor connector pins for oxidation, blackening, backing out, deformation, or enlarged holes. Clean with electrical contact cleaner. If necessary, use a terminal removal tool to repair the pins or replace the connector housing. Verify the sealing ring is intact.
  • 6
    Sensor replacement and refrigerant system handling: If the sensor is faulty, first recover the air conditioning system refrigerant. Use the special tool to remove the old sensor; note the thread seal. Install the new sensor and a new sealing washer, then tighten to the specified torque (usually 15-20 N·m). Evacuate the system for at least 30 minutes to a vacuum below -95 kPa. Recharge the system with the standard amount of refrigerant and compressor oil.
  • 7
    Function verification and road test: Clear the fault code, start the vehicle, and turn on the A/C cooling mode. Read the data stream to verify the plate heat exchanger refrigerant temperature sensor value drops normally as the compressor operates (normal range: -10°C to 50°C). Perform a DC fast charging test to confirm the battery thermal management system engages normally and sets no new fault codes.
Real-World Cases
BYD DTC AI Analysis

The Qin EV suddenly entered limp mode while driving, logging DTC B2A0F13.

✓
A 2019 BYD Qin EV with 82,000 km. Customer reported that while driving at highway speeds, the dashboard suddenly displayed "Power Limited, Please Park Safely" and the coolant temperature high warning light came on. Retrieved DTC B2A0F13 (current fault). Inspection found the plate heat exchanger refrigerant temperature sensor wiring harness had chafed against the metal edge of the front bulkhead penetration due to long-term vibration, wearing through the insulation and severing the copper conductors. Repair: Cut out the damaged harness section and soldered in high-temperature wire of the same specification (125°C minimum rating), applied double-layer heat shrink tubing, rerouted the harness and added a rubber grommet to prevent recurrence. Road tested after repair; live data showed normal refrigerant temperature and the fault cleared.
BYD DTC AI Analysis

Battery pack high temperature warning during fast charging; sensor internal open circuit

✓
2019 BYD Qin EV. After 10 minutes of fast charging, the dashboard displayed "Battery temperature too high" and charging power suddenly dropped below 5 kW. The scanner retrieved DTC B2A0F13; freeze frame data showed the refrigerant temperature at -40°C (default open-circuit extreme value) when the fault occurred. Sensor resistance read infinite, indicating an open circuit in the internal NTC thermistor. The sensor sits at the refrigerant outlet of the plate heat exchanger, operating under long-term high pressure (1.5–3.0 MPa) and temperature cycling. Replaced the sensor, then evacuated the AC system and recharged it with 450 g of R410a refrigerant. Post-repair fast charging test confirmed the battery temperature stayed below 35°C; fault resolved.
BYD DTC AI Analysis

Intermittent DTCs after accident repair, loose connector

✓
A Qin EV involved in a front-end collision was repaired at a dealership. Afterward, the vehicle intermittently set DTC B2A0F13 while driving, accompanied by intermittent AC cooling loss. Technicians found the plate heat exchanger temperature sensor connector had not fully seated during the collision repair. While it appeared connected externally, the male and female terminals inside had poor contact, causing momentary open circuits over bumps. Repair: Disconnected the connector and found the female contacts slightly enlarged. Resized the terminals using a special tool, applied conductive paste, and reconnected until a distinct click confirmed the lock. Secured the harness to the bracket with a cable tie to eliminate stress. Monitored for one week with no fault recurrence.
BYD DTC AI Analysis

Corrosion of the sensor connector on the water-damaged vehicle caused an open circuit

✓
A Qin EV in the southern region threw code B2A0F13 on startup the day after driving through floodwater. Inspection revealed the vehicle had waded deeper than the wheel centers, submerging the front compartment wiring harness. The plate heat exchanger temperature sensor connector (located in the lower front compartment) contained standing water, with pins showing green copper corrosion and white electrolytic corrosion that caused an open circuit. Repair: Disconnected the battery negative terminal and thoroughly cleaned the connector using precision electronic cleaner and ultrasonic cleaning, then dried it. The corrosion had damaged the pin plating, so replaced the sensor harness assembly (including the connector) to eliminate any risk of recurrence. Applied waterproof silicone grease to other low-position connectors for protection.
Other Seal 6 EV Fault Codes
B1108For 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.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.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.
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.