UAE
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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.

3
Cases Logged
Real-World Cases
BYD DTC AI Analysis

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

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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.
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BYD DTC AI Analysis

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

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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.
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BYD DTC AI Analysis

BYD Qin Early Charging Termination (Abnormal Voltage Detection Reference)

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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.
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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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.