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 — Atto 3

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 — Atto 3
  • 1Loose sensor wiring harness connector or poor contact: Long-term vibration in the high-temperature, high-humidity environment of the front compartment causes terminal back-out or locking tab failure.
  • 2Internal open circuit in the pressure sensor: Refrigerant pressure shock, liquid slugging, or aging damaged the sensor diaphragm or internal circuit.
  • 3Physical damage to the wiring harness: The front compartment wiring harness rubbing against sharp body edges, rodents chewing the harness, or excessive bending during accident repairs, causing the copper strands to break.
  • 4Blown fuse: Sensor power supply circuit fuse (typically 5V reference voltage or 12V power supply) blown (e.g., IF11, IF12).
  • 5ECU connector oxidation: Oxidized pins or enlarged sockets at 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). 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 recessed pins. Inspect the wiring harness corrugated 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). If the resistance is infinite, replace the sensor. 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). Carefully inspect intermediate connectors (such as the front compartment harness to instrument panel harness connector and the front compartment harness to front bumper harness connector).
  • 5
    Insulation and short-circuit check: Measure signal wire resistance to ground and check for a short to power. Eliminate hidden faults where harness wear causes 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 hold test, and recharge the system (standard amount: approximately 600-800g R134a or R1234yf). Use the diagnostic tool to read the pressure sensor data stream. Verify the displayed value matches the actual pressure (0.2-3.5 MPa range) without fluctuation.
  • 7
    System function test: Start the vehicle, turn on the A/C cooling and battery cooling modes, and verify the pressure sensor live data changes normally. Confirm the fault code does not return. 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 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.