AU
B16AC-00

DTC B16AC-00 indicates an internal hardware or software fault in the airbag control unit (SRS ECU), specifically a malfunction in the ECU internal processor, memory, power management circuit, or reference voltage circuit — Qin Plus

Safety System

DTC B16AC-00 indicates an internal hardware or software fault in the airbag control unit (SRS ECU), specifically a malfunction in the ECU internal processor, memory, power management circuit, or reference voltage circuit.

This core control module fault may cause the airbags to fail to deploy during a collision or deploy unintentionally in non-collision situations, severely compromising occupant passive safety.

Abnormal ECU internal voltage regulation circuits (5V reference voltage fluctuation), main control chip (e.g., NXP SPC5604) processor errors, crystal oscillator failure, internal memory data corruption, or lost configuration parameters typically cause this fault, rather than external sensor or wiring harness issues.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Internal ECU water ingress and corrosion: A blocked or restricted A/C drain hose causes condensation to seep under the center console. Poor SRS ECU housing sealing exposes the internal circuit board to moisture, causing a short in the voltage regulator circuit or corroding the chip pins.
  • 2Power supply system fault: Improper power-off procedures during high-voltage system or 12V battery repairs cause voltage surges that impact the internal ECU power management module, or prolonged low voltage causes abnormal processor operation.
  • 3Physical hardware damage: Cold solder joints on the main control chip BGA, stopped 32.768kHz crystal oscillator, resonant capacitor failure, or PCB interlayer short circuit. This typically occurs in vehicles with no collision history but subjected to vibration or severe temperature changes.
  • 4Software defects and configuration loss: Corrupted ECU internal Flash data, missing VIN or configuration parameters, or software bugs (e.g., early V2.1 version) triggering an internal fault during self-check.
  • 5External short circuit: A short to ground or power in the crash sensor wiring harness or seat belt pretensioner wiring harness triggers the ECU protection circuit and records an internal fault code.
What To Do
  • 1
    Connect the diagnostic tool (Launch X-431 or BYD VDS) and access the SRS system. Read and record all fault codes. Confirm B16AC-00 is a current fault and cannot be cleared. Check for accompanying fault codes (such as B1696, B1684, etc.).
  • 2
    Check the ECU power supply system: Measure the voltage at SRS ECU connector terminal B16 (constant power); it should be 12V. Measure the voltage at terminal B1 (IGN power); it should be 12V with the ignition ON. Verify the ground harness connection is secure. Measure the CAN-H (2.6V) and CAN-L (2.4V) communication voltages to verify they are normal.
  • 3
    Inspect the ECU exterior: Remove the SRS ECU from under the center console (first disconnect the battery negative terminal and wait 3 minutes). Check the housing seal for aging, the PCB for water ingress, corrosion, or burn marks, and the connector lock for looseness or pin oxidation.
  • 4
    Perform software diagnostics: Attempt ECU online programming or a software upgrade using OEM equipment. Check for missing internal configuration data (VIN, airbag configuration code). Back up the old data if readable.
  • 5
    Replace or repair the ECU: If inspection confirms internal hardware damage, install a new SRS ECU (note the hardware version number) or send the unit to an electronics repair shop for BGA rework (resolder the main control chip and replace the crystal oscillator). Never use salvage parts.
  • 6
    Online configuration and calibration: Use ED400 or Autel MS908 to execute the 'Replace ECU' procedure. Write the vehicle VIN, configuration parameters, and crash sensor sensitivity parameters. Perform seat occupancy sensor (OCS) calibration and seat belt pretensioner matching.
  • 7
    System verification: Clear all fault codes, perform an SRS system self-check, and confirm B16AC-00 does not return. Verify the instrument cluster SRS warning lamp turns off normally. Perform a simulated crash test (using special equipment) to verify normal airbag communication.
Real-World Cases
BYD DTC AI Analysis

Qin Pro SRS ECU water damage case

✓
The 2017 Qin Pro's SRS warning light illuminated suddenly after driving in the rain. The diagnostic tool retrieved DTCs B16AC-00 (SRS ECU fault) and B1696-00. Inspection confirmed no collision history. Removing the SRS ECU from beneath the centre console revealed slight water ingress marks on the housing. Measuring the internal voltage regulator circuit revealed abnormal fluctuation in the 5V reference voltage. Further inspection found the air conditioning drain hose blocked, allowing condensation to leak inside. Solution: Replaced the airbag control unit (BYD-3638100), recoded the module, wrote the VIN, and cleared the AC drain hose to prevent further water ingress. Repair cost approximately 1050 yuan.
Original source ↗
BYD DTC AI Analysis

ECU processor damaged after windscreen replacement on Song Plus

✓
During normal driving, the BYD Song PLUS instrument cluster displayed 'Check Airbag System' and the passenger seatbelt warning light flashed erratically. The system had stored DTCs B16AC-00 and B1684-00 (OCS system fault). The customer reported a recent front windscreen replacement. We found the SRS ECU connector lock loose. We measured the power supply and found it normal, but the ECU self-test showed 'Internal Fault - Processor Error'. We determined that improper power disconnection during the windscreen replacement damaged the processor. We replaced the SRS ECU with a new assembly (4A-3638100A). Using specialised equipment, we performed the ECU replacement procedure, read the coding data from the old ECU and wrote it to the new unit, performed a system self-test, and resolved the fault.
Original source ↗
BYD DTC AI Analysis

Tang DM airbag control module main board chip-level repair

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At 80,000 km, the SRS warning light suddenly illuminated on a 2018 BYD Tang DM. The vehicle logged DTCs B16AC-00 and U0146-00 (lost communication with gateway). The 4S dealership recommended replacing the ECU assembly and quoted ¥3,800. The owner instead took the car to a specialist electronics repair shop. Technicians found the main control chip (NXP SPC5604) had cold BGA solder joints. An oscilloscope check showed the 32.768 kHz crystal oscillator had stopped oscillating. The shop re-soldered the main control chip using a BGA rework station, replaced the SMD crystal oscillator (12.5 pF load capacitance), cleaned the PCB, and applied conformal coating. After reinstalling the unit, they performed online configuration with an Autel MS908. This cleared the fault and restored the airbag system. The repair cost ¥600, a saving of ¥3,200 compared to replacing the ECU.
Original source ↗
BYD DTC AI Analysis

Improper power-off procedure causes software fault on Yuan EV

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2019 BYD Yuan EV360. After battery pack repair, the SRS light stayed on constantly. DTCs B16AC-00 and B1693-00 present (poor ground connection). Owner found the technician had improperly disconnected the 12V battery negative terminal. Checking the SRS ECU power supply fuse (F1/14, 10A) revealed an oxidised fuse holder. Cleaning cleared B1693-00, but B16AC-00 remained. An online ECU software update failed. The dealership confirmed a software bug in this ECU batch (hardware version V2.1). Solution: Ordered and fitted a new SRS ECU (hardware version V2.3), performed online configuration to write VIN and airbag settings, calibrated Occupant Classification System (OCS) and impact sensors, and cleared fault codes. SRS light went out.
Original source ↗
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.