AU
B2ABB-17

This fault code indicates the voltage on the high-voltage side of the electric air conditioning compressor exceeds the controller's safety threshold (typically 750V-800V DC, depending on the vehicle's high-voltage platform) — Atto 3

Thermal Management System

This fault code indicates the voltage on the high-voltage side of the electric air conditioning compressor exceeds the controller's safety threshold (typically 750V-800V DC, depending on the vehicle's high-voltage platform).

The system triggers the high-voltage interlock protection mechanism to prevent overvoltage breakdown of the compressor's internal power semiconductors (IGBT or SiC modules).

When the BMS or compressor controller detects the bus voltage momentarily or continuously exceeds the calibrated upper limit, it logs this fault and limits or disables compressor operation.

This causes a loss of air conditioning cooling and heating functions and, in extreme cases, triggers reduced-power operation of the vehicle's high-voltage system.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Traction battery pack voltage spikes momentarily at the end of DC fast charging or during heavy regenerative braking, exceeding the compressor controller upper tolerance limit.
  • 2Internal voltage sampling circuit fault in the A/C compressor high-voltage controller (ACCM), such as voltage divider resistor drift or Hall sensor miscalibration causing false fault detection.
  • 3Welded or stuck main positive or main negative contactor in the high-voltage power distribution unit (PDU) causes uneven voltage distribution and generates voltage spikes.
  • 4Loose or burnt compressor high-voltage wiring harness connector (usually located near the right longitudinal rail in the front compartment) causes excessive contact resistance, triggering momentary overvoltage.
  • 5Outdated vehicle software version, overly sensitive voltage threshold calibration, or unsynchronized detection caused by BMS communication delay.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (ED-400/ED-500) to read the detailed fault data stream. Record the bus voltage, SOC status, and ambient temperature at the time of the fault to distinguish a genuine overvoltage from a false sampling reading.
  • 2
    Check the consistency between the traction battery pack total voltage and individual cell voltages. Perform the BMS active balancing test using the diagnostic tool to rule out a false high total voltage caused by individual cell overcharging.
  • 3
    Disconnect the Manual Service Disconnect (MSD) and wait 5 minutes. Inspect the A/C compressor high-voltage harness connector (usually orange, located on the right side of the front compartment) for burn marks, water ingress, or looseness. Measure the insulation resistance between the terminals (should be >500MΩ).
  • 4
    Power on the system again. With the air conditioning on, use a multimeter to measure the actual voltage at the compressor high-voltage input terminal and compare it with the diagnostic tool reading. If the deviation exceeds ±5%, replace the compressor controller.
  • 5
    Check the contactor status inside the high-voltage Power Distribution Unit (PDU). Measure the voltage drop across the contactor terminals. If the voltage drop is >50mV when closed, replace the contactor assembly.
  • 6
    If the hardware inspection reveals no faults, update the air conditioning controller (ACCM) and BMS software to the latest version, then recalibrate the high-voltage side voltage threshold.
  • 7
    Clear the fault code. Perform a DC fast charging and full-load air conditioning operation test (recommend at least 30 minutes) to confirm the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

AC Compressor Not Working After Fast Charging: Case Report

✓
A 2018 Qin PRO DM fast-charged to 95% at a DC charging station. Turning on the air conditioning triggered DTC B2ABB-17 and the AC stopped cooling. Diagnosis found the fault occurred the instant fast charging ended: battery pack voltage hit 712V (nominal 653V), exceeding the compressor controller's 750V protection threshold. Inspection found the BMS charging cut-off voltage calibration was off. Updated BMS software to V2.3, correcting the charging cut-off voltage to 705V. Fault resolved.
BYD DTC AI Analysis

Poor contact in the high-voltage harness caused transient overvoltage

✓
While driving, the air conditioning on a 2019 Qin Pro EV suddenly cut out and the dashboard displayed a thermal management fault. Data logs showed the bus voltage spiked to 820V when the fault occurred (actual battery voltage was only 620V). Inspection found the internal spring clip in the compressor high-voltage connector had loosened, increasing contact resistance and generating an induced voltage spike under the compressor's start-up current surge. Replaced the high-voltage harness and applied conductive paste. Monitored for two weeks with no recurrence.
BYD DTC AI Analysis

Compressor controller sampling circuit fault

✓
2017 BYD Qin EV300 repeatedly threw DTC B2ABB-17. Bus voltage measured only 640V—well below the 750V threshold. Disassembled the compressor controller: the internal voltage sampling divider resistors (100kΩ/1% tolerance) had drifted to 107kΩ from prolonged heat exposure, causing the controller to falsely flag overvoltage. Replaced the electric compressor assembly (integrated controller and compressor). Fault resolved. Advised owner to avoid prolonged fast charging in extreme heat.
BYD DTC AI Analysis

Software mismatch after high voltage distribution box replacement

✓
After collision repairs, a Qin PRO DM had its high-voltage distribution box (PDU) replaced. The vehicle then set intermittent fault code B2ABB-17. Diagnosis revealed an approximately 200ms delay between the new PDU's contactor closure timing and the ACCM voltage sampling sequence, causing the sampling to capture voltage spikes from contactor bounce. Reflashing the ACCM software and adjusting the voltage sampling filter time constant from 10ms to 50ms completely resolved the fault.
BYD DTC AI Analysis

False positive fault in low temperature conditions

✓
Northern winter case: Qin EV300 set DTC B2ABB-17 on cold start at -15°C; cleared after 10 min driving. Data stream analysis showed increased battery internal resistance in the cold. ACCM sampling circuit captured overshoot voltage during voltage-drop recovery as the AC engaged. Software calibration boundary case. Fix: ACCM software update adding low-temperature compensation (voltage threshold raised 20V when ambient temp <-10°C).
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.