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 6 EV

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 6 EV indicates an internal hardware or software fault in the airbag control unit, potentially causing airbag deployment failure or unintended deployment. Severity is medium. Common causes include water ingress from blocked A/C drains corroding internal circuits, or voltage surges during improper battery disconnection damaging the power management module. Visiting an authorised dealer is recommended. Typical repair cost data is available from four recorded cases.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 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 voltage regulator circuit short or chip pin corrosion.
  • 2Power supply system fault: Improper power disconnection when servicing the high-voltage system or 12V battery generates a voltage surge that damages the ECU internal 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. Typically occurs in vehicles with no collision history but exposed to severe vibration or extreme temperature changes.
  • 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 self-check to report an internal fault.
  • 5External short circuit effect: A short to ground or short to 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 will not clear. 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) with the ignition in the ON position; it should be 12V. Verify the ground wiring harness connection is secure. Measure the CAN-H (2.6V) and CAN-L (2.4V) 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 diagnosis: 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 diagnostics confirm internal hardware damage, replace the unit with a brand-new SRS ECU (verify 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). Do not use salvage parts.
  • 6
    Online configuration and calibration: Use the ED400 or Autel MS908 to perform 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 recur. Check that the instrument cluster SRS warning light turns off normally. Perform a simulated crash test (using dedicated 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

✓
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 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Seal 6 EV →Seal 6 EV 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.