AU
B2A1113

This DTC indicates an open circuit in the refrigerant pressure sensor signal circuit at the plate heat exchanger (Chiller/battery cooler) of the thermal management system — Seal U

Thermal Management System

This DTC indicates an open circuit in the refrigerant pressure sensor signal circuit at the plate heat exchanger (Chiller/battery cooler) of the thermal management system.

The sensor monitors the refrigerant pressure flowing through the plate heat exchanger and serves as a key feedback component for the battery thermal management and cabin air conditioning systems.

An open circuit causes the ECU to receive an open-circuit voltage (typically the saturated 5V reference voltage or 0V), preventing it from acquiring actual pressure data.

This forces the thermal management control unit to enter fail-safe mode, which limits battery fast-charging power, disables the battery cooling function, and reduces drive motor power.

In extreme cases, this fault triggers a battery high-temperature warning or shuts down the high-voltage system, severely impacting vehicle safety and driving range.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose sensor wiring harness connector or poor contact: Long-term vibration in the high-temperature and high-humidity environment of the front compartment causes terminal back-out or latch failure.
  • 2Open circuit inside the pressure sensor body: Refrigerant pressure shock, liquid slugging, or aging damaged the sensor diaphragm or internal circuit.
  • 3Physical damage to the wiring harness: Front compartment wiring harness rubbing against sharp body edges, rodent damage, or excessive bending during accident repairs, causing copper wire breakage.
  • 4Blown fuse: Sensor power supply circuit fuse (typically 5V reference voltage or 12V power supply) is blown (e.g., IF11, IF12).
  • 5ECU connector oxidation: Oxidized pins or enlarged sockets on the thermal management controller or air conditioning controller cause excessive contact resistance in the signal circuit, which the system detects as an open circuit.
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS2000/VDS3000 to read DTC B2A1113 and freeze frame data. Confirm the ambient temperature and pressure sensor voltage at the time of the fault (usually 4.9-5.0V or 0V), and check for accompanying DTCs (e.g., a concurrent B2A1212 short circuit fault indicates an intermittent wiring harness fault).
  • 2
    Visual inspection: Inspect the pressure sensor connector near the plate heat exchanger (usually located on the battery cooler outlet pipe) for looseness, water ingress, corrosion, or backed-out pins. Inspect the corrugated wiring harness conduit for damage or signs of chafing against nearby sharp edges.
  • 3
    Sensor component measurement: Disconnect the connector. Measure the resistance between the sensor signal pin and the ground pin (normal resistance falls within a specific range, such as 0.5-4.5kΩ, varying with pressure). Replace the sensor if the resistance is infinite. Measure the sensor supply voltage (specification: 5V±0.25V).
  • 4
    Harness continuity check: Use a multimeter to measure harness continuity between the sensor connector and the thermal management controller (or air conditioning controller). Focus on intermediate connectors (such as the front compartment harness to instrument panel harness mating connector, and the front compartment harness to front bumper harness mating connector).
  • 5
    Insulation and short circuit check: Measure signal wire resistance to ground and check for shorts to power. Rule out hidden faults caused by harness chafing resulting in a short to ground or power.
  • 6
    Component replacement and verification: After replacing the faulty sensor or repairing the wiring harness, clear the fault code, evacuate the refrigerant system, perform a pressure holding test, and recharge the system (standard amount approximately 600-800g R134a or R1234yf). Use the diagnostic tool to read the pressure sensor data stream to confirm the displayed value matches the actual pressure (0.2-3.5MPa range) and does not fluctuate.
  • 7
    System function test: Start the vehicle, turn on the air conditioning cooling and battery cooling modes, and verify the pressure sensor live data changes normally. Confirm the fault code does not recur. Perform a road test to verify the thermal management system operates normally.
Real-World Cases
BYD DTC AI Analysis

Worn front compartment wiring harness causing intermittent open circuit on Qin EV

✓
A 2019 Qin EV with 80,000 km showed an intermittent "Thermal Management System Fault" warning. DTC B2A1113 (intermittent). The plate heat exchanger pressure sensor harness had chafed against a metal edge at the front compartment firewall opening, wearing through the insulation and partially severing the copper strands. Vibration caused intermittent contact. Repair: Cut out the damaged section, soldered in an extension, added corrugated tubing, and repositioned the clips to prevent interference. Replaced the damaged connector terminals. Fault resolved.
BYD DTC AI Analysis

Sensor connector seal failed, causing water ingress and corrosion

✓
After the vehicle drove through water, DTC B2A1113 set and would not clear. Disconnected and inspected the refrigerant pressure sensor connector at the plate heat exchanger. The waterproof seal had deteriorated and was missing, and the pins inside the connector had oxidized and turned green, causing poor contact on the signal wire. As this is a three-wire sensor (5V reference, signal, ground), the oxidation effectively created an open circuit on the signal line. Solution: Replaced the pressure sensor with wiring harness plug assembly. Cleaned and applied anti-corrosion treatment to the controller-side connector. Rewrapped with waterproof tape. Fault resolved.
BYD DTC AI Analysis

Loose connector following accident repair caused open circuit

✓
A post-accident repair Qin EV lit the warning light and set DTC B2A1113 the day after dealership delivery following front bumper and condenser replacement. Inspection found the plate heat exchanger pressure sensor connector wasn't fully seated; the locking clip wasn't engaged, so vibration shook it loose. Fix: Reconnected the connector firmly until the locking click, cleared the fault codes, and used a scan tool to verify normal pressure signal in live data (approximately 0.6–0.8 MPa at idle).
BYD DTC AI Analysis

Sensor internal circuit damaged

✓
The vehicle suddenly set DTC B2A1113 during normal operation. Harness continuity and 5V supply both normal. Removed the refrigerant pressure sensor at the plate heat exchanger; measured infinite resistance (normal: 200Ω–4kΩ varying with pressure). Internal pressure-sensitive element or circuit board burned out from abnormal high-pressure surge in the refrigerant system. Replaced with OEM refrigerant pressure sensor (part number typically HA-XXX series). Also checked expansion valve and electric compressor control logic to prevent damage to the new sensor. Fault cleared.
Other Seal U 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.