AU
B2A5113

DTC B2A5113 indicates an open circuit in the signal circuit of the A/C system low-pressure line pressure-temperature (PT) sensor — Atto 3

Thermal Management System

DTC B2A5113 indicates an open circuit in the signal circuit of the A/C system low-pressure line pressure-temperature (PT) sensor.

This sensor typically mounts on the low-pressure line between the evaporator outlet and the compressor inlet.

It monitors low-side refrigerant pressure and temperature in real time, providing a key input signal to the heat pump/A/C control unit (integrated into the right domain controller or A/C controller) for compressor speed regulation, system protection, and thermal management.

When the controller detects the sensor signal voltage continuously exceeding the normal range (typically 0.5-4.5V) or a communication interruption, it sets this open circuit fault.

The system then triggers a protection mechanism and forces the electric compressor to stop, resulting in a complete loss of A/C cooling and heating functions.

In extreme cases, this affects the battery pack cooling circuit and creates an overheating risk.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Internal open circuit in the low-pressure line pressure sensor body (damaged pressure-sensing element, broken internal solder joint, or open coil)
  • 2Poor contact at the sensor connector (terminal back-out, oxidation/corrosion, or loose retaining clip causing an intermittent connection)
  • 3Physical damage to the wiring harness (wear at the firewall pass-through, detached harness clip causing contact with the vehicle body and wearing through the insulation, corrosion and breakage after water ingress)
  • 4Severe refrigerant loss in the air conditioning system causes excessively low low-side pressure, triggering sensor limit protection (false open circuit).
  • 5Control unit sampling circuit fault (damaged internal signal processing chip in the right domain controller or air conditioning controller, sampling resistor open circuit)
What To Do
  • 1
    Safety preparation: Disconnect the low-voltage battery negative terminal, wait at least 5 minutes to ensure the high-voltage system discharges completely, and wear insulated gloves and safety goggles.
  • 2
    Fault confirmation: Connect the VDS diagnostic tool, read the fault code, record the freeze frame data, and confirm whether the B2A5113 status is active or historical.
  • 3
    Visual inspection: Locate the low-pressure line pressure sensor (located on the low-pressure side of the air conditioning line in the front compartment, usually with a 2-3 pin connector). Check the connector for looseness, water ingress, or oxidation. Inspect the wiring harness for obvious damage or crush marks.
  • 4
    Circuit measurement: Disconnect the sensor connector, turn the ignition switch ON, and measure the voltage at the connector power supply pin (expected: 5V±0.25V reference voltage). Measure the signal pin voltage to ground. Turn the ignition switch OFF and measure the sensor resistance (typically hundreds to thousands of ohms at room temperature; refer to the specific vehicle repair manual for standard values).
  • 5
    Wiring harness continuity test: Disconnect the controller connector. Use a multimeter to measure continuity between the sensor connector signal pin and the corresponding controller pin. Resistance must be less than 1 Ω, and insulation resistance to ground must be greater than 10 MΩ.
  • 6
    System pressure verification: Connect a manifold gauge set to the high- and low-pressure service ports and check the static pressure (normal readings approximate the saturation pressure for the ambient temperature, e.g., 1.5-1.8 MPa at 25°C). If the low-pressure side reads close to 0 or indicates a vacuum, the system is severely low on refrigerant.
  • 7
    Component replacement: If the sensor is damaged, replace it with a genuine low-pressure line pressure sensor. (Note: Recover the refrigerant before replacement. After replacement, evacuate the system for more than 30 minutes, then recharge the refrigerant and compressor oil to the standard amount.)
  • 8
    Wiring harness repair: If there is an open circuit, repair the harness using waterproof heat-shrink tubing. Re-secure the harness routing to prevent contact with sharp edges.
  • 9
    Function verification: Clear the fault code, start the vehicle, and set the air conditioning to maximum cooling mode. Observe the VDS data stream to verify the low-pressure value fluctuates normally with compressor speed (normal range: 0.2-0.5 MPa). Confirm the compressor operates normally and the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

BYD Han EV new car AC not cooling (factory refrigerant undercharge)

✓
Han EV purchased new in November 2020. Customer reported the air conditioning failed to cool on first use, with only ambient air from the vents. VDS scan retrieved DTC B2A2F09 (AC line pressure abnormal), B2A4E16 (high-pressure line pressure sensor open circuit) and B2A5113 (low-pressure line pressure sensor open circuit). Live data showed the compressor had not started. Measured normal supply voltage at the pressure sensors with no resistance anomalies. Manifold gauge testing revealed the system contained no refrigerant. Pressurized leak testing found no leaks. Determined the vehicle left the factory without refrigerant. Fix: Evacuated the system and recharged with the standard quantity of R134a refrigerant (approximately 650g). Fault resolved and air conditioning cooling returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD e2: Intermittent air-con cooling failure (poor connector contact)

✓
A BYD e2 at 30,000 km suddenly lost AC cooling after running for a while, though restarting sometimes restored it. VDS detected B2A5113 (low-pressure line pressure sensor open circuit) and B2A2F09 (line pressure abnormal) in the integrated body controller. The data stream showed erratic low-pressure readings. Removing the low-pressure line pressure sensor connector revealed terminals that had backed out slightly; the connector latch had worked loose, letting vibration cause intermittent contact. Repair: Reseated the terminals using a terminal removal tool, reconnected the connector with conductive grease, and cable-tied the harness to relieve strain. Fault has not recurred.
Original source ↗
BYD DTC AI Analysis

BYD Qin Plus EV: Poor cooling performance (damaged sensor unit)

✓
Customer reported the Qin Plus EV air conditioning set to minimum temperature (17°C), but three vents still read 21°C with significantly reduced cooling performance. VDS scan of the right domain controller (integrating the AC control unit) revealed stored fault code B2A5113 for low-pressure line pressure sensor open circuit. Live data showed low-side pressure at 0.05 MPa (abnormally low), while the manifold gauge measured 0.35 MPa (normal), pointing to internal sensor damage causing signal distortion. Fix: Recovered refrigerant, replaced the low-pressure line pressure sensor, evacuated the system and recharged refrigerant. Test drive confirmed vent temperatures dropped to 6°C; fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM intermittent air conditioning failure (connector oxidation)

✓
New-generation Tang DM. After normal use, parked for 2 hours, then the air conditioning again failed to cool. No dashboard warning lights, but the compressor would not run. Drove normally in EV mode. VDS scan showed B2A5113 currently present. Checked the low-pressure line pressure sensor and found green oxide inside the connector. Sensor power supply measured 5V (normal), but signal line output voltage fluctuated 0–5V. Connector oxidation increased contact resistance and interrupted signal transmission. Fix: Cleaned the connector terminals with precision electrical contact cleaner, applied conductive anti-oxidant grease, reconnected and waterproofed. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro EV air conditioning system fault (wiring harness chafing, open circuit)

✓
Vehicle AC completely inoperative; compressor not starting. VDS scan showed multiple HVAC DTCs including B2A5113 (low-pressure line pressure sensor open circuit). Power supply at sensor connector normal, but signal line from connector to controller measured open (infinite resistance). Traced wiring and found harness chafing against a sharp metal edge where it passes through the firewall. Insulation worn through, internal signal wire completely broken with copper core exposed. Repair: Opened harness, resoldered broken conductor, applied multiple layers of heat-shrink tubing, rerouted harness and added rubber grommet and cable ties to prevent body contact. Fault resolved.
Original source ↗
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.