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 — Seal U

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.

The B16AC-00 fault code on the Seal U indicates a medium-severity internal fault in the airbag control unit (SRS ECU), affecting its processor, memory, or power circuits. This may cause airbags to fail to deploy or deploy unexpectedly. Common causes include water ingress from a blocked A/C drain hose corroding the ECU, or voltage surges from improper battery disconnection. Visit an authorised dealer for repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Internal ECU water ingress and corrosion: A blocked or restricted A/C drain hose allows condensation to seep under the center console. Poor SRS ECU housing sealing allows moisture to reach the internal circuit board, causing a short circuit in the voltage regulator circuit or corrosion of the chip pins.
  • 2Power supply system fault: Improper power-off procedures when servicing the high-voltage system or 12V battery generate voltage surges that impact the internal ECU power management module, or prolonged low voltage causes abnormal processor operation.
  • 3Physical hardware damage: dry solder joints on the main control chip BGA, stalled 32.768kHz crystal oscillator, resonant capacitor failure, or PCB interlayer short circuit. This typically occurs in vehicles with no collision history but exposed to vibration or severe temperature fluctuations.
  • 4Software defects and configuration loss: Corrupted ECU internal Flash data, missing VIN or configuration parameters, or software bugs (such as early V2.1), causing the ECU to report an internal fault during self-check.
  • 5External short circuit impact: A short to ground or power in the crash sensor wiring harness or seat belt pretensioner wiring harness triggers the ECU protection circuit and logs 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).
  • 2
    Check the ECU power supply system: Measure the voltage at SRS ECU connector terminal B16 (constant power); it should be 12 V. Terminal B1 (IGN power) should be 12 V with the ignition ON. Verify the ground wiring harness connection is secure. Measure the CAN-H (2.6 V) and CAN-L (2.4 V) communication voltages to confirm they are normal.
  • 3
    Remove and inspect the ECU exterior: Remove the SRS ECU beneath the center console (disconnect the battery negative terminal and wait 3 minutes first). Check the housing seal for aging. Check the PCB for signs of water ingress, corrosion, or burn marks. Check the connector lock for looseness and the pins for oxidation.
  • 4
    Perform software diagnostics: Attempt ECU online programming or software upgrade using OEM equipment. Check if internal configuration data (VIN, airbag configuration code) is missing. Back up old data if readable.
  • 5
    Replace or repair the ECU: If testing confirms internal hardware damage, replace the unit with a new SRS ECU (note the hardware version number) or send it to an electronics repair shop for BGA rework (resolder the main control chip and replace the crystal oscillator). Never use salvaged parts.
  • 6
    Online configuration and calibration: Use the 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 the SRS system self-check, confirm B16AC-00 does not return, verify the instrument cluster SRS warning lamp turns off normally, and 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

✓
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 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.