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 8

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 8
  • 1During the final stage of DC fast charging or strong regenerative braking, the traction battery pack voltage spikes momentarily, exceeding the compressor controller's maximum tolerance.
  • 2Internal voltage sampling circuit fault in the air conditioning compressor high-voltage controller (ACCM), such as voltage divider resistor drift or Hall sensor miscalibration causing a false code.
  • 3Main positive or negative contactor in the high-voltage power distribution unit (PDU) welds or sticks, causing uneven voltage distribution and generating voltage spikes.
  • 4A loose or burnt compressor body high-voltage wiring harness connector (usually located near the right longitudinal beam in the front compartment) causes excessive contact resistance and triggers momentary overvoltage.
  • 5Outdated vehicle software, 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, and ambient temperature at the time of the fault to determine whether the overvoltage is genuine or a sampling error.
  • 2
    Check the consistency between the traction battery pack total voltage and individual cell voltages. Use the diagnostic tool to perform the BMS active balancing test to rule out an artificially high total voltage caused by cell overcharging.
  • 3
    Disconnect the Manual Service Disconnect (MSD) and wait 5 minutes. Inspect the air conditioning compressor high-voltage harness connector (typically orange, located on the right side of the front compartment) for burning, water ingress, or loose connections. Measure the insulation resistance between the terminals (should be >500MΩ).
  • 4
    Power on the system again. Turn on the air conditioning. Use a multimeter to measure the actual voltage at the compressor high-voltage input terminal. Compare this measurement with the value displayed on the diagnostic tool. 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 hardware tests normal, update the air conditioning controller (ACCM) and BMS software to the latest version, and recalibrate the high-voltage side voltage threshold.
  • 7
    Clear the fault code and perform a DC fast charging and full-load air conditioning test (minimum 30 minutes recommended) 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 8 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.