AU
B16B000

DTC B16B000 indicates the airbag electronic control unit (SRS ECU) detects an internal system fault or a deployment circuit abnormality — Seal U

Safety System

DTC B16B000 indicates the airbag electronic control unit (SRS ECU) detects an internal system fault or a deployment circuit abnormality.

This fault may involve an internal ECU processor fault, a power/ground abnormality, a CAN communication fault, or, more commonly, the driver-side airbag deployment circuit resistance falling outside the calibrated range (normal 2.0-3.0 Ω).

When the ECU detects high circuit resistance (>5 Ω), an open circuit, low circuit resistance (<1 Ω), or a short circuit, it sets this code and illuminates the instrument cluster airbag warning lamp.

The system enters fail-safe mode, and the airbag may fail to deploy during a collision.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Clock spring (spiral cable) internal ribbon cable broken or poor contact: Repeated steering wheel rotation wears the internal flat cable, causing an intermittent or permanent open circuit.
  • 2Airbag module ignition circuit fault: Broken internal clock spring after a collision, oxidized connector, or internal module open circuit, causing abnormal circuit resistance.
  • 3Wiring harness water corrosion: Waterproofing failure on the under-seat or floor wiring harness allows water to enter the connector, producing verdigris and causing increased contact resistance or signal interference.
  • 4Improper modification or repair: Unprofessional steering wheel removal and installation causing incorrect clock spring positioning, excessive tension on the airbag wiring harness, or damaged connector locking tabs.
  • 5Internal SRS ECU fault: damaged power supply chip, internal memory data error, or burnt ignition driver circuit (common in accident-damaged vehicles or under abnormal voltage conditions)
What To Do
  • 1
    Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS ECU capacitor to fully discharge. Do not work on the airbag system with the ignition switch in the ON position.
  • 2
    Diagnostic scan: Use BYD VDS2000 or ED400 to read complete fault codes and freeze frame data. Confirm if the fault is stored or current. Check the 'DAB Resistance' (driver airbag resistance) value in the data stream.
  • 3
    Visual inspection: Check the yellow connector (airbag-specific colour) under the steering wheel for looseness or backed-out terminals, inspect the clock spring for visible damage, and verify the waterproof plugs on the under-seat and floor wiring harnesses are intact.
  • 4
    Circuit resistance measurement: Use a dedicated airbag system tester or a multimeter connected in series with a 2kΩ resistor to measure the driver airbag circuit resistance (disconnect the ECU connector and measure the resistance on the wiring harness side; normal range: 2.0-3.0Ω). Never directly measure the airbag squib using a multimeter ohm setting.
  • 5
    Isolation test: Disconnect the pocket plug. Measure the resistance on both sides of the clock spring separately to determine whether the clock spring or the airbag module is faulty. If the resistance is infinite, replace the clock spring. If the module side has an open circuit, replace the airbag assembly.
  • 6
    Special handling for water-damaged vehicles: If the wiring harness shows corrosion, replace the entire harness section instead of only cleaning the connector. Rewrap the harness using waterproof tape (3M Scotch 33+) and heat-shrink tubing. Install a waterproof protective sleeve if necessary.
  • 7
    ECU matching and calibration: If replacing the SRS ECU or airbag module, use the diagnostic tool to perform the 'Replace ECU' or 'Airbag Configuration' function, write the VIN and configuration code, and perform sensor zero-point calibration.
  • 8
    Clear and verify: Reconnect the battery, start the vehicle, and confirm the airbag warning light turns off after the self-check (within 6 seconds). Turn the steering wheel lock-to-lock, then road test the vehicle to confirm the intermittent fault does not recur.
Real-World Cases
BYD DTC AI Analysis

BYD Qin PLUS DM-i clock spring poor contact

✓
Symptoms: Dashboard airbag warning light constantly on with audible chime. Diagnosis: VDS2000 retrieved DTC B16B000. Measured driver airbag circuit resistance at 5.8Ω (out of specification). On disassembly, found the white clock spring connector had poor contact with oxidised pins. Repair: Cleaned connector pins, applied conductive paste and reassembled. Resistance returned to 2.4Ω, fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro DM module fault after accident repair

✓
Symptoms: After front collision repairs, the airbag warning light stayed on constantly and could not be cleared. Diagnosis: DTCs B16B000 and B16B100 stored. Measured infinite resistance (open circuit) at the driver-side airbag module. The collision impact fractured the clock spring inside the airbag. Repair: Replaced the driver-side airbag assembly (EQ-5820100), performed ECU matching and system calibration. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM-i wiring harness corrosion due to water ingress

✓
Symptoms: After water ingress, the dashboard displayed a "Check Airbag System" warning. Diagnosis: Retrieved DTC B16B000. Inspected the wiring harness connector under the seat and found the waterproof seal had detached. Internal water staining and verdigris were present, with resistance fluctuating between 2–10 Ω. Resolution: Replaced the driver's side airbag wiring harness (clock spring to ECU section), rewrapped the connections with waterproofing, and fitted a waterproof protective sleeve.
Original source ↗
BYD DTC AI Analysis

Modified steering wheel caused a fault in a BYD Han EV.

✓
Symptoms: After fitting an aftermarket carbon fibre steering wheel and driving 500 km, the airbag light came on. There were abnormal noises when turning the wheel at a standstill. Diagnosis: DTC B16B000. Disassembly revealed that excessive pulling on the airbag harness had broken the yellow plug locking tab, and that the clock spring locating pin was misaligned, damaging the clock spring. Resolution: Replaced the OE clock spring (HCE-5820100), repaired the harness plug, and refitted the original steering wheel.
Original source ↗
BYD DTC AI Analysis

BYD Yuan EV360 intermittent fault

✓
Symptoms: Warning light occasionally illuminates on cold start and turns off automatically after 10–15 minutes of driving. Diagnosis: Historic DTC B16B000. Circuit readings normal when warm. Determined poor contact in clock spring at low temperatures. Disassembly revealed dried internal grease, causing poor contact between slip ring and brush when cold. Repair: Replaced clock spring assembly. Fault completely resolved.
Original source ↗
Other Seal U 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.