AU
B2ABA1C

DTC B2ABA1C indicates a fault in the internal low-voltage DC power conversion module of the electric air conditioning compressor (E-Compressor) controller — Qin Plus

Thermal Management System

DTC B2ABA1C indicates a fault in the internal low-voltage DC power conversion module of the electric air conditioning compressor (E-Compressor) controller.

This module converts the vehicle 12V battery voltage to 5V/3.3V to power the main control MCU, temperature sensor, current sensor, and LIN/CAN communication chips on the compressor control board.

The controller sets this code when the internal DC-DC conversion circuit output voltage falls outside the permitted range (typically below 4.5V or above 5.5V), triggers short-circuit protection, or sustains a MOSFET breakdown.

This fault disables the compressor control logic and prevents it from responding to air conditioning start commands.

This directly affects cabin cooling/heating and the battery pack liquid cooling circuit, but does not compromise high-voltage drive system safety.

The B2ABA1C fault code on the Qin Plus indicates a medium-severity fault in the electric A/C compressor controller’s internal low-voltage DC power module. This can stop the compressor from responding, affecting cabin climate control and battery cooling. Common causes include a failed MOSFET or filter capacitor, or unstable 12V supply voltage. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Aging and breakdown of the MOSFET or filter capacitor in the compressor controller's internal DC-DC power module causes an abnormal 5V output.
  • 2Intermittent open circuit or voltage fluctuation (below 9V or above 16V) in the 12V low-voltage supply circuit causes a protective lockout of the internal power module.
  • 3Compressor controller seal failure allowing condensate or moisture ingress, causing internal circuit board short circuit or corrosion.
  • 4Controller PCB soldering defect (cold solder joint issue in specific batches), causing an open circuit after prolonged thermal cycling.
  • 5Controller overheating (poor heat dissipation) under extreme operating conditions triggers internal power supply thermal protection or causes thermal damage to components.
What To Do
  • 1
    Connect the BYD dedicated diagnostic tool (ED-400 or Launch X-431), read the complete DTC freeze frame data, and confirm B2ABA1C is a current fault (Present), not a history fault.
  • 2
    Check the compressor low-voltage connector: measure the 12V supply (PIN1/2) voltage; it must be between 12.0-14.5V. Verify the LIN line (PIN3) resistance to ground is approximately 60Ω. Confirm no backed-out pins, oxidation, or signs of water ingress.
  • 3
    Read data stream: Check parameters including compressor controller internal temperature (normal <70°C), high-voltage side voltage (320V-420V), and IGBT temperature to rule out related faults.
  • 4
    Disconnect the compressor low-voltage connector and use an oscilloscope to check the 12V power supply ripple. If the ripple voltage is >500mV, first inspect and repair the front compartment power distribution box or the BCM power supply circuit.
  • 5
    If the external power supply is normal, diagnose an internal compressor controller fault. BYD electric compressors feature a fully sealed integrated design, preventing separate repair of the internal power module. Replace the compressor assembly (part numbers vary by vehicle model, e.g., BC28E-8103020 for the Qin EV).
  • 6
    After replacement, perform the following: ① Evacuate the system using a vacuum pump (hold at <-95kPa for 10 minutes); ② Charge R134a refrigerant to standard specification (usually 450-550g); ③ Use a diagnostic tool to execute the 'A/C system initialization' or 'compressor self-learning' procedure; ④ Road test the vehicle and observe compressor speed response and high-voltage interlock status.
Real-World Cases
BYD DTC AI Analysis

Qin Pro EV compressor internal power module breakdown

✓
Vehicle AC suddenly stopped cooling. No warning lights on the instrument cluster, but the AC panel flashed. Scan tool retrieved DTCs B2ABA1C (current fault) and B2AB573 (startup failure). Measured compressor HV at 320V (normal), 12V supply normal, LIN signal normal. Disassembled the compressor controller; internal 5V DC-DC module output measured only 1.2V and the MOSFET had shorted. Replaced the electric compressor assembly; fault resolved. Old unit analysis confirmed the power module filter capacitor had insufficient voltage rating, causing breakdown—a quality issue from an early production batch.
BYD DTC AI Analysis

Intermittent B2ABA1C and high temperature protection on Song PLUS EV

✓
Owner reported AC cutting in and out during hot weather; fixed by restarting. Intermittent DTC B2ABA1C accompanied by B2AB64B (internal temperature abnormal). Found compressor mounted too close to exhaust manifold with poor heat dissipation. Data stream showed controller temperature reaching 85°C triggered protection. Disassembly revealed bulging, leaking electrolytic capacitor in internal power module and excessive compressor bearing resistance. Replaced compressor and optimized mounting bracket (added thermal insulation pad). Issue resolved.
BYD DTC AI Analysis

BYD Yuan Plus batch low-voltage power supply defect recall

✓
Certain batches of Yuan Plus (SC2E) suffered clustered AC cooling failures. Diagnostics reported DTC B2ABA1C. BYD confirmed via technical bulletin that specific supplier batches of the compressor controller PCBA had cold solder joints, causing the internal power module to open-circuit under vibration. The manufacturer issued a technical upgrade, replacing compressors on faulty vehicles with improved versions (controller V2.3 or higher) free of charge and extending the warranty on related components.
BYD DTC AI Analysis

BYD Dolphin New Car Early Failure Warranty Claim Case

✓
AC failed at 4,800 km. DTC B2ABA1C present. Checked high-voltage interlock and 12V supply — both normal. 12V input at the compressor low-voltage connector measured normal, but the LIN line had no signal feedback (should send periodic messages). Diagnosed a manufacturing defect in the compressor controller's internal power module that prevented the MCU from starting. Processed the warranty claim, replaced the compressor assembly and recharged the refrigerant. Fault resolved.
BYD DTC AI Analysis

e-Platform 3.0 Vehicle Software False Alarm Troubleshooting

✓
Found history DTC B2ABA1C at routine service. Owner reported no AC issues. No active faults present; compressor operating normally. Early software version produces false codes during voltage fluctuations (e.g., jump-starting a discharged battery). Cleared codes, updated compressor controller software to latest version via VDS2000, and checked 12V battery health (replace if SOC < 50%).
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus overview →
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.