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B16B0

DTC B16B0 indicates the Airbag Control Unit (SRS ECU) internal self-diagnosis detected a critical function abnormality — Qin Plus

Safety System

DTC B16B0 indicates the Airbag Control Unit (SRS ECU) internal self-diagnosis detected a critical function abnormality.

This ECU integrates the main control MCU, backup power supply, crash sensors (accelerometers), and ignition driver circuit.

An "internal fault" specifically refers to compromised ECU core hardware or firmware integrity, including internal voltage regulator module failure (e.g., 5V/3.3V reference voltage deviation), EEPROM data checksum errors, interrupted communication between the main and backup CPUs, crash sensor signal processing circuit faults, or ignition loop driver chip damage.

This fault forces the airbag system into fail-safe mode.

During a collision, the system may fail to deploy airbags or activate seat belt pretensioners.

It also carries a risk of unintended deployment, classifying it as a highest-level safety-related fault.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

2019 Song MAX SRS ECU internal power supply module burned out

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Customer reported the SRS warning light on the instrument cluster stayed on constantly. Scan tool retrieved DTC B16B0. Vehicle history showed the battery went flat and was jump-started a week earlier, possibly with reverse polarity. Removed and inspected the ECU; found the internal fuse blown and pin 12 of the power management chip (TLE7368) burnt. Reverse voltage breakdown had shorted the 5V regulator output. Replaced the SRS ECU (part number BYD-3638100) and reconfigured — fault cleared. Advised the customer to check the jump-start procedure.
BYD DTC AI Analysis

Internal ECU corrosion in flood-damaged BYD Qin Pro DM

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After driving through water, the dash displayed 'Check Airbag System'. Read fault codes B16B0 and B16B1. Removed the SRS ECU from the centre of the floor and found the housing seal had deteriorated, allowing water in. The PCB showed multiple areas of copper trace corrosion and bulging capacitors. Cleaned and attempted to dry the unit, but the fault persisted. Determined the internal accelerometer signal conditioning circuit had corroded open. Replaced the ECU and treated the water stains on the wiring harness. Fault resolved. Recommend checking the A/C drain tube for blockage.
BYD DTC AI Analysis

Petrol Qin software version defect causing false positives

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2020 Qin petrol variant, no accident history or water ingress. SRS light came on intermittently, pulled intermittent DTC B16B0. Checked ECU power and earth – normal, no external damage. Looked up the TSB (Technical Service Bulletin) and found this ECU batch (hardware version H02, software version V1.03) has an internal watchdog reset defect. Upgraded software to V1.05 and the fault has not reappeared. This is a typical firmware bug, not hardware damage.
BYD DTC AI Analysis

Song MAX internal sensor fault after accident repair

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Following front collision repairs (front bumper and left front longitudinal member replaced), the SRS warning light stayed on, storing DTC B16B0. The airbag did not deploy in the original accident, but the ECU likely experienced a high G-force impact. Using a diagnostic scanner, we read the internal acceleration sensor data stream and found the X-axis signal fixed at -12.8g (normal: 0±0.5g), indicating physical damage to the internal sensor. No external cracks were visible, but the MEMS structure had failed. Replacing the ECU and performing collision threshold calibration resolved the issue.
BYD DTC AI Analysis

Long-term vibration caused cold solder joints on the BGA.

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A Song MAX rideshare vehicle with 180,000 km on the clock intermittently displayed an SRS warning light; DTC B16B0 came and went. Power supply was normal. Tapping the ECU housing reproduced the fault. We stripped down the ECU and performed BGA rework on the main controller chip (Renesas RH850) using a hot air rework station. After reballing and resoldering, the fault cleared. The root cause was solder joint fatigue from prolonged driving on rough roads. Rideshare operators should regularly inspect the chassis and ECU mounting bracket vibration dampers.
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.