AU
B2A5113

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

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 — Seal U
  • 1Internal open circuit in the low-pressure line pressure sensor body (damaged pressure-sensitive element, detached internal solder joint, or open coil)
  • 2Poor contact at the sensor connector (terminal back-out, oxidation/corrosion, or loose locking clip causing intermittent connection)
  • 3Physical damage to the wiring harness (wear at the firewall pass-through hole, detached harness retaining clips causing interference with the body and chafing through the insulation, corrosion and breakage after water ingress)
  • 4Severe refrigerant loss in the air conditioning system causes excessively low pressure on the low-pressure side, 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, open sampling resistor)
What To Do
  • 1
    Safety preparation: Disconnect the low-voltage battery negative terminal, wait at least 5 minutes for the high-voltage system to fully discharge, 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 a history fault.
  • 3
    Visual inspection: Locate the low-pressure line pressure sensor (on the low-pressure side of the A/C lines in the front compartment, usually with a 2-3 pin connector). Inspect the connector for looseness, water ingress, or oxidation, and inspect the wiring harness for obvious damage or crush marks.
  • 4
    Circuit measurement: Disconnect the sensor connector and turn the ignition switch ON. Measure the voltage at the connector power supply pin (expected reference voltage: 5V±0.25V). Measure the voltage between the signal pin and ground. Turn the ignition switch OFF. Measure the sensor resistance (typically several hundred to several thousand ohms at room temperature; refer to the specific vehicle repair manual for standard values).
  • 5
    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 check: Connect a manifold gauge set to the high- and low-pressure service ports and check the static pressure (normal pressure approaches the saturation pressure for the ambient temperature, e.g., approximately 1.5-1.8 MPa at 25°C). If the low-pressure side reads near 0 or shows negative pressure, the system is severely low on refrigerant.
  • 7
    Component replacement: If the sensor body is damaged, replace it with an OEM low-pressure line pressure sensor. (Note: Recover the refrigerant before replacement. After replacement, evacuate the system for at least 30 minutes, then recharge the specified amount of refrigerant and compressor oil.)
  • 8
    Wiring harness repair: If an open circuit exists, repair the wiring harness using waterproof heat-shrink tubing. Re-secure the harness routing to prevent contact with sharp edges.
  • 9
    Function check: Clear the fault code, start the vehicle, and set the air conditioning to maximum cooling mode. Monitor 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 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.