AU
B2A0716

The internal voltage monitoring circuit in the Air Conditioning Control Unit (ACU) or Integrated Thermal Management System (ITMS) controller triggers DTC B2A0716 — Atto 3

Thermal Management System

The internal voltage monitoring circuit in the Air Conditioning Control Unit (ACU) or Integrated Thermal Management System (ITMS) controller triggers DTC B2A0716.

This indicates the supply voltage in power circuit 161 (typically the constant B+ or IG ignition supply for the air conditioning module) falls below the 9V operating threshold.

This fault signifies a low-voltage supply abnormality in the thermal management system.

Upon detecting insufficient operating voltage, the controller logs the fault and may enter a degraded protection mode.

This mode limits the electric compressor speed, shuts off the PTC heater, or halts electronic expansion valve operation, reducing or disabling air conditioning cooling and heating functions.

In extreme cases, this condition affects the traction battery cooling circuit and triggers overheat protection.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1An aged or discharged 12V low-voltage battery, or an excessive cold-start voltage drop, causes the air conditioning controller supply voltage to momentarily drop below 9V.
  • 2Air conditioning controller power supply fuse (IF08/IF09) in the front compartment power distribution box or instrument panel power distribution box is blown, has poor contact, or the fuse holder is burnt.
  • 3Air conditioning controller wiring harness connector (e.g., connector G06/JA01) is loose, oxidized, corroded by water ingress, or has backed-out terminals, causing increased contact resistance.
  • 4Poor connection in the power supply circuit, damaged wiring harness, or spliced aftermarket equipment causing excessive circuit voltage drop (>3V) under high-current operating conditions.
  • 5Faulty air conditioning controller internal power management chip, DC-DC conversion circuit, or voltage sampling resistor, causing false alarms or voltage regulation failure.
What To Do
  • 1
    Use the VDS2000/VDS1000 diagnostic tool to scan all vehicle systems, confirm B2A0716 is the current fault code, and record the freeze frame data (voltage at time of occurrence, ambient temperature, etc.).
  • 2
    Measure the 12V battery static voltage (≥12.4V) and the minimum voltage at startup (≥9.6V). Check the battery state of health (SOH ≥80%). Replace the battery if necessary.
  • 3
    Check the air conditioning system fuses (IF08, IF09, etc.) in the front compartment power distribution box and the instrument panel power distribution box. Confirm there are no blown fuses or loose connections. Measure the voltage drop across the fuse holders (should be <0.1V).
  • 4
    Disconnect the A/C controller harness connector. With the ignition ON, measure the voltage to ground at the power supply pins (constant B+ and IG power) and compare it to the battery terminal voltage. The voltage difference must be <0.5 V.
  • 5
    Check the wiring harness connector pins for oxidation, backed-out terminals, or enlarged pin holes. Measure the power supply circuit resistance (should be <1Ω) and the insulation resistance to ground (should be >10MΩ).
  • 6
    Perform a load test: Connect the diagnostic tool to read the data stream. Turn on the A/C MAX mode and observe whether the controller feedback voltage drops below 9V to confirm the fault reproduction conditions.
  • 7
    If wiring and power supply are normal, replace the air conditioning controller assembly (part number must match vehicle configuration). Complete online programming and coding configuration, clear fault codes, and road test to verify.
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX: Intermittent A/C cooling failure with DTC B2A0716

✓
Air conditioning occasionally cut out while driving. Instrument panel showed no warning lights, but cooling stopped. VDS read current fault code B2A0716 (Power Supply Voltage Undervoltage). 12V battery tested normal. Voltage measured at air conditioning controller JA01 connector pins 17 (B+) and 18 (IG) dropped instantly from 12.4V to 8.5V when the vehicle hit bumps. Disassembly revealed burning and loose connection inside fuse holder IF08 of the front compartment power distribution box, causing excessive contact resistance. Replaced front compartment power distribution box assembly and repaired wiring harness terminals. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM on-board charger DC-side low voltage fault (P157216)

✓
Customer reported vehicle would not charge and showed abnormal charging power after connecting the charging gun. VDS read DTC P157216 (on-board charger DC-side voltage low, same undervoltage category as B2A0716). On-board charger low-voltage supply measured at 8V during charging. Found oxidized pins on the charger low-voltage connector. Cleaned and tightened the connector. Supply voltage restored to 12V. Charging function normal. Same fault mechanism as B2A0716: insufficient control module supply voltage restricting function.
Original source ↗
BYD DTC AI Analysis

BYD Qin Early Charging Termination (Abnormal Voltage Detection Reference)

✓
Charging stopped automatically at around 10%, with the dash showing charging interrupted. Testing showed the BMS (Battery Management System) communicating normally with the charger, but the BMS detected abnormally low total voltage sampling, triggering a protective shutdown. The fault traced to poor contact in the BMS slave module sampling harness causing voltage detection errors. Repaired the harness and updated BMS software; fault cleared. This case shows how voltage detection abnormalities affect system function, with technical relevance to B2A0716 voltage monitoring logic.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.