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B16C3

DTC B16C3 indicates a functional fault in the airbag system electronic control unit (SRS_ECU) — Qin Plus

Safety System

DTC B16C3 indicates a functional fault in the airbag system electronic control unit (SRS_ECU).

The SRS_ECU is the core controller of the safety system.

It monitors crash sensor signals in real time, processes crash algorithms, controls the deployment timing of the airbags and seat belt pretensioners, and manages the communication network of the entire passive safety system.

This DTC usually indicates an internal processor or memory fault in the ECU, or a loss of communication between the ECU and the vehicle CAN network.

An intermittent open circuit in the ECU power supply or ground circuit can also trigger this fault.

This fault causes the airbag system to enter fail-safe mode.

The airbags may fail to deploy in a collision, creating a serious safety risk.

3
Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX: Faulty evaporator temperature sensor caused air conditioning failure

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Poor A/C cooling, vent temperature not low enough, intermittent compressor operation. VDS scan found DTC B2A2F09 (evaporator temperature sensor fault). Data stream showed evaporator temperature fixed at –40°C (clearly abnormal). Further inspection revealed backed-out pins in the evaporator temperature sensor connector causing poor contact. Re-secured the sensor connector pins and cleared the fault code. Data stream returned to normal and A/C cooling function was restored.
Original source ↗
BYD DTC AI Analysis

BYD Qin DM: A/C compressor not starting

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After turning on the A/C, no cold air blew from the vents, the compressor did not start, and the recirculation/fresh air switching was inoperative. The owner initially ran an OBD scan and found multiple communication fault codes in the climate control system. Inspection at the dealership confirmed an abnormal power supply to the HVAC control module. The A/C compressor fuse in the engine bay fuse box had blown. Replacing the fuse did not fix the fault. Further investigation revealed an internal short circuit in the A/C pressure switch, triggering system protection. After replacing the pressure switch, the compressor worked normally and the fault was fully resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro automatic A/C temperature control fault

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The fault symptoms were a significant discrepancy between the set temperature and actual air outlet temperature, a noticeable temperature difference between the left and right air vents, and abnormal fan speed adjustment in AUTO mode. A dealership technician used a scan tool to retrieve fault codes related to the temperature blend door actuator. Checking the live data from each temperature sensor, the technician found the cabin temperature sensor reading deviated from the actual ambient temperature by about 15°C. The technician diagnosed a failed cabin temperature sensor (located inside the dashboard). The repair involved replacing the cabin temperature sensor and recalibrating the blend door actuator using the scan tool. After the repair, temperature control accuracy returned to normal.
Other Qin Plus 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.