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 8

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.

The B2A0716 fault code on the Atto 8 indicates low supply voltage to the air conditioning or thermal management controller, falling below about 9V. Severity is medium because cooling, heating, or battery cooling may be reduced or disabled. Common causes include an aging or discharged 12V battery, voltage drop during start-up, or a blown/poor-contact A/C power fuse. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 112V low-voltage battery aging, discharge, or excessive voltage drop during cold start causes the air conditioning controller power supply to momentarily drop below 9V.
  • 2A/C controller power supply fuse (IF08/IF09) in the front compartment distribution box or instrument panel distribution box blown, poor contact, or burnt fuse holder base.
  • 3Loose connection, backed-out terminals, oxidation, or water ingress corrosion at the air conditioning controller wiring harness connector (e.g., plug G06/JA01), causing increased contact resistance.
  • 4Poor connection in the power supply circuit, damaged wiring harness, or aftermarket equipment spliced into the circuit causing the line voltage drop to exceed the limit (>3V) under high-current operating conditions.
  • 5Faulty air conditioning controller internal power management chip, DC-DC conversion circuit, or voltage sampling resistor, causing false reporting or failure to stabilize voltage.
What To Do
  • 1
    Scan the entire vehicle system using the VDS2000/VDS1000 diagnostic tool, confirm B2A0716 is a current fault code, and record the freeze frame data (voltage at the time of occurrence, ambient temperature, etc.).
  • 2
    Measure the 12V battery static voltage (≥12.4V) and 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 instrument panel power distribution box. Confirm the fuses are not blown and the connections are secure. Measure the voltage drop across the fuse holders (should be <0.1V).
  • 4
    Disconnect the air conditioning controller wiring harness connector. With the vehicle in the ON state, measure the voltage to ground at the power supply pins (constant B+ and IG power) and compare it with the battery terminal voltage. The voltage difference must be < 0.5V.
  • 5
    Check wiring harness connector pins for oxidation, backed-out terminals, or enlarged pin holes. Measure power supply circuit resistance (should be <1 Ω) and insulation resistance to ground (should be >10 MΩ).
  • 6
    Perform a load test: Connect the diagnostic tool to read the data stream, set the A/C to MAX mode, and observe if the controller feedback voltage drops below 9V to confirm the fault reproduction conditions.
  • 7
    After confirming 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 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.