AU
B132317

This DTC indicates the air conditioning system control unit or a thermal management-related module detects its operating supply voltage exceeds the 16V threshold (BYD low-voltage system rated voltage: 12V; normal operating range: 9–16V) — Atto 8

Thermal Management System

This DTC indicates the air conditioning system control unit or a thermal management-related module detects its operating supply voltage exceeds the 16V threshold (BYD low-voltage system rated voltage: 12V; normal operating range: 9–16V).

This is an overvoltage protection fault.

When the module detects an abnormal rise in supply voltage, it stores this DTC and may enter protection mode, limiting air conditioning or thermal management functions to prevent electronic component damage.

Overvoltage typically stems from abnormal output from the low-voltage charging system (DC-DC converter), alternator voltage regulator failure (hybrid models), or abnormal power supply circuit impedance.

Prolonged overvoltage may burn out the control module internal circuits or damage the compressor driver.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1DC-DC converter fault: The internal voltage regulation circuit in the high-voltage to low-voltage DC-DC module fails, causing the output voltage to exceed 16V. This is the most common cause.
  • 2Severe low-voltage battery aging: Increased internal resistance or plate sulfation prevents the battery from accepting normal current during charging, causing the terminal voltage to rise abnormally.
  • 3Generator voltage regulator fault (hybrid models): ISG motor or generator controller fault causes unregulated charging voltage.
  • 4Poor power wiring harness contact: A loose or oxidized positive wiring harness connector or poor ground point contact changes circuit impedance, causing the module to detect a falsely high voltage.
  • 5Air conditioning control module sampling circuit fault: An abnormal internal A/D conversion circuit or voltage divider resistor triggers a false overvoltage fault.
What To Do
  • 1
    Use a high-precision multimeter to measure the low-voltage battery static and dynamic voltages (when applying the A/C load). Confirm whether the actual voltage exceeds 16V to rule out a false fault.
  • 2
    Connect the VDS diagnostic tool to read the data stream. Check the 'System Voltage' data stream in the air conditioning module or thermal management module to confirm whether the overvoltage is continuous or intermittent.
  • 3
    Check the DC-DC converter output voltage: With the vehicle in READY mode, measure the voltage at the DC-DC output terminal. Normal voltage is 13.8-14.5V. If the voltage exceeds 16V, replace the DC-DC assembly.
  • 4
    Check the low-voltage battery state of health: Use a battery tester to measure the CCA value and internal resistance. If the internal resistance exceeds 5mΩ or the capacity is below 50%, replace the 12V battery.
  • 5
    Check power supply circuit integrity: Check the A/C control module constant power (B+), ignition power (IG), and ground (GND) connectors. Specifically inspect the wiring harness from the instrument panel distribution box to the A/C module for oxidation or poor connections.
  • 6
    Check relevant fuses and relays: Inspect the air conditioning system fuses (usually located in the instrument panel fuse box and engine compartment fuse box) for proper contact and burn marks.
  • 7
    If hardware inspection reveals no faults, update or reflash the air conditioning control module software to rule out false warnings caused by software calibration.
  • 8
    If all above checks are normal, replace the air conditioning control module or thermal management control unit and perform coding.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro DM: DC-DC converter abnormal output caused air conditioning failure

✓
2018 Qin Pro DM, 62,000 km. Dashboard showed 'Thermal Management System Fault', AC not cooling, read DTC B132317. Measured the low-voltage battery: 17.2 V and unstable. Disconnected the DC-DC low-voltage output connector; battery voltage returned to 12.4 V. Measured DC-DC output terminals: voltage fluctuated between 16.5–17.8 V, confirming internal voltage regulation circuit failure. Replaced the DC-DC converter assembly (part no. EA-2141000C), cleared fault codes, road tested. Output voltage stabilized at 14.2 V, AC operation normal.
BYD DTC AI AnalysisFrom Chinese market (translated)

Battery aging causes intermittent overvoltage fault in Qin EV300

✓
Vehicle: 2017 Qin EV300, 98,000 km. Intermittent automatic A/C shut-off, the instrument cluster illuminated the coolant over-temperature warning light, and DTC B132317 stored as a history code. Static voltage measured 12.6V (normal), but voltage spiked to 16.8V upon power-on. The 12V battery tested at 8.5mΩ internal resistance with only 38% capacity remaining. Severe plate sulfation prevented normal charge current acceptance, causing the DC-DC converter output voltage to rise. Replaced the battery with a new AGM unit (12V 60Ah). The DTC has not returned, and the thermal management system operates normally.
BYD DTC AI AnalysisFrom Chinese market (translated)

Poor contact in the dashboard power distribution box caused the A/C module to detect overvoltage.

✓
Vehicle: 2019 Qin Pro EV, 45,000 km. Symptom: Intermittent AC shutdown while driving, with DTC B132317. System recovered after restart. Repair: Measured AC control module supply voltage. Found ignition (IG) voltage fluctuating between 16.2–16.8 V while battery terminal voltage remained normal at 14.1 V. Inspected instrument panel fuse box and found burn marks on fuse holder F2-15 (AC module power). Increased contact resistance caused abnormal voltage division. Cleaned the fuse box terminals, replaced the fuse, and applied conductive grease to the fuse holder. Module supply voltage returned to normal 13.8 V. Fault cleared.
BYD DTC AI AnalysisFrom Chinese market (translated)

Reflashed the air conditioning controller to resolve a software false alarm.

✓
Vehicle: 2019 BYD Qin Pro DM, 31,000 km. No actual symptoms, but the scan tool read historic DTC B132317. The owner reported a brief episode of A/C not cooling. Measured low-voltage system voltage throughout the test: normal at 13.5-14.4V. DC-DC converter worked normally, auxiliary battery health good. Suspected the HVAC control module had outdated software with a voltage sampling algorithm bug. Updated the HVAC controller software using VDS3000 from V1.2 to V1.5. Cleared DTCs after the update. Followed up for 1 month — no DTC recurrence. This confirmed a software false positive.
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. Sources: [1]