AU
B2A0716

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

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 Seal U indicates low supply voltage to the Air Conditioning Control Unit or ITMS controller, below the 9V operating threshold. Severity is medium, as heating, cooling, compressor, PTC heater, or battery cooling performance may be limited. Common causes include a weak or discharged 12V battery, voltage drop during start-up, or a blown/poor-contact AC controller power fuse. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 112V low-voltage battery degradation, discharge, or excessive voltage drop during cold start 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 blown, poor contact, or burnt fuse holder.
  • 3Loose connection, backed-out terminals, oxidation, or water ingress corrosion at the air conditioning controller wiring harness connector (such as the G06/JA01 plug), causing increased contact resistance.
  • 4Poor connection in the power supply circuit, damaged wiring harness, or spliced aftermarket equipment causing line voltage drop to exceed the limit (>3V) under high-current operating conditions.
  • 5Fault in the air conditioning controller internal power management chip, DC-DC conversion circuit, or voltage sampling resistor, causing false reporting or failure to regulate voltage.
What To Do
  • 1
    Use the VDS2000/VDS1000 diagnostic tool to scan all vehicle systems, confirm B2A0716 is a current fault code, and record freeze frame data (voltage at 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 the instrument panel power distribution box. Verify there are no blown fuses or loose connections. 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 from the power supply pins (constant B+ and IG power) to ground and compare it with the battery terminal voltage. The voltage difference must be <0.5V.
  • 5
    Check the wiring harness connector pins for oxidation, backed-out terminals, or enlarged terminals. Measure the 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. Turn on the air conditioning 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 perform a 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 Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.