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B2A5112

DTC B2A5112 indicates a short circuit in the thermal management system Pressure Transducer (PT) — Seal U

Thermal Management System

DTC B2A5112 indicates a short circuit in the thermal management system Pressure Transducer (PT).

Specifically, the signal circuit shorts to power or ground (BYD DTC subtype definition '12' typically indicates a short to power).

This sensor mounts in the air conditioning high-pressure line or battery coolant circuit.

It monitors refrigerant or cooling system pressure in real time, providing key parameters to the thermal management controller (TMS) or air conditioning controller to regulate electric compressor speed, electronic expansion valve opening, and cooling fan speed.

During a short circuit, the controller loses accurate pressure readings and enters fail-safe mode.

This can disable the air conditioning, reduce battery cooling, and trigger motor over-temperature protection.

In severe cases, the system limits drive power or disables driving to prevent critical component damage from thermal management failure.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1PT pressure sensor internal short circuit: Overvoltage, aging, or manufacturing defects cause an internal short circuit in the pressure-sensitive element or signal processing circuit, shorting the signal wire directly to power or ground.
  • 2Wiring harness wear or crush damage: Chafing from vibration, sharp edges, or bottoming out damages the sensor wiring harness insulation in the engine compartment or under the chassis, shorting the signal wire (usually the 5V reference voltage wire) to the 12V power wire or body ground.
  • 3Connector water ingress and corrosion: An aged sensor plug seal, an improperly seated plug, or water ingress after washing or wading causes electrolytic corrosion between pins, creating a short circuit. This fault occurs frequently in humid environments.
  • 4Internal control unit circuit fault: Filter capacitor breakdown or sampling resistor burnout in the signal acquisition circuit of the thermal management controller or air conditioning controller causes the 5V reference voltage to short to ground or to the 12V power supply.
  • 5Improper repair work: During recent air conditioning system repairs (such as replacing the compressor or condenser), failing to connect the sensor connector correctly, or improperly routing the wiring harness, causing a metal bracket to pinch and damage the harness, resulting in a short circuit.
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code. Confirm B2A5112 is a current fault (Present), not a history fault. Record the freeze frame data, including ambient temperature, compressor speed, and pressure sensor voltage at the time of the fault, to determine whether it is an intermittent fault or a continuous short circuit.
  • 2
    Visual and connector inspection: Disconnect the low-voltage service switch to ensure high-voltage safety. Inspect the PT pressure sensor connector (located at the A/C high-pressure line or battery cooling line connection) for backed-out pins, signs of water ingress, burning, or corrosion. Measure the resistance between the connector pins to verify no abnormal continuity.
  • 3
    Circuit continuity and short circuit test: Disconnect the air conditioning controller or thermal management controller connector. Use a multimeter to measure the resistance from the sensor signal wire (usually connector Pin2) to ground and to the 12V power supply. The normal reading is infinite. If continuity exists, inspect the wiring harness along its routing, specifically checking mounting points, the firewall pass-through, and areas contacting metal parts. Repair any damaged insulation.
  • 4
    Sensor unit inspection: Remove the PT pressure sensor and measure the resistance between its power supply pin (usually 5V reference voltage) and the signal pin. Normal resistance values correspond to specific pressure ranges (refer to the workshop manual: 0.5-4.5V corresponds to 0-3.5MPa). Replace the sensor if the resistance is 0 or infinite, or if the signal wire has continuity with the power or ground wire.
  • 5
    Load test and system verification: After replacing the sensor or repairing the wiring harness, clear the fault code, start the vehicle, and set the air conditioning to maximum cooling. Observe the data stream to verify the pressure sensor voltage rises from approximately 0.5V to 1.5-2.5V (corresponding to 0.2-1.5MPa) during compressor operation. Perform a 30-minute road test to confirm the fault code does not return, and inspect for refrigerant leaks.
Real-World Cases
BYD DTC AI Analysis

Air conditioning failure after water wading in BYD Qin EV300 with DTC B2A5112

✓
A 2017 Qin EV300 displayed 'Air Conditioning System Fault' after driving through deep water in heavy rain. Retrieved fault code B2A5112 (PT pressure sensor short circuit). Found water inside the air conditioning high-pressure line pressure sensor connector located forward of the right front wheel arch liner. Pin 3 (signal wire) and Pin 1 (5V reference) shorted due to electrolytic corrosion. Cleaned and dried the connector, applied conductive grease, and cleared the fault. Check the waterproof seals on sensor connectors for this model and apply waterproof tape if necessary.
BYD DTC AI Analysis

Wiring harness pinched after air conditioning repair caused intermittent short circuit

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The vehicle set DTC B2A5112 after electric compressor replacement; fault was intermittent. Troubleshooting found the PT pressure sensor harness incorrectly routed between the compressor bracket and body from the previous repair. Driving vibration wore through the insulation, causing the signal wire to intermittently short to ground. Re-routed the harness, wrapped the damaged section with flame-retardant tape, and adjusted the path to avoid sharp edges. Fault eliminated. Note: Check wiring harness clip integrity after any thermal management system repair.
BYD DTC AI Analysis

Internal short circuit in the sensor caused thermal management failure.

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Qin EV300 suddenly limited power while driving and the motor overheating warning light came on. Scanner showed active fault code B2A5112. At the sensor connector, 5V reference was normal but the signal line stayed at 5V (should vary 0.5-4.5V). Sensor internal signal circuit shorted to power. Replaced the air conditioning pressure sensor (part number EG-8121100). Data stream showed normal pressure values and the system regulates compressor speed normally. Fault resolved.
BYD DTC AI Analysis

Controller internal fault caused false detection of sensor short circuit

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Fault code B2A5112. With the sensor disconnected, the wiring harness tested normal. After replacing the sensor, the fault remained. Further inspection revealed the filter capacitor in the AC controller's signal acquisition circuit had broken down, shorting the 5V reference voltage to ground. The controller misread this as a sensor short. Replaced the thermal management controller (integrated in the AC control unit) and flashed the software to the latest version (post-2018 releases optimized the short-circuit detection threshold). Fault eliminated. Distinguish between sensor shorts and controller detection circuit failures.
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.