AU
B17841A

This fault code indicates the SRS control module detects the driver-side front airbag Stage 2 igniter (inflator) circuit resistance at or near 0 ohms, indicating a short circuit (short to ground or short between wires) — Seal U

Safety System

This fault code indicates the SRS control module detects the driver-side front airbag Stage 2 igniter (inflator) circuit resistance at or near 0 ohms, indicating a short circuit (short to ground or short between wires).

In dual-stage airbag systems, Stage 2 typically provides additional inflation capacity during severe collisions or delays inflation to optimize protection.

A resistance of 0 ohms causes the SRS ECU to determine the igniter circuit is abnormal.

The ECU disables the deployment function of this airbag stage and illuminates the airbag warning light.

In extreme cases, an unstable short circuit creates a risk of unintended airbag deployment, or the airbag stage may fail to inflate normally during an actual collision, reducing protection and severely compromising occupant safety.

The B17841A fault code on the Seal U indicates a short circuit in the driver-side front airbag Stage 2 igniter circuit, with resistance near 0 ohms. Severity is medium, but it can disable that airbag stage and affect crash protection. Common causes include a worn or damaged clock spring or an internal fault in the driver airbag module. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1The clock spring (spiral cable) internal conductor breaks and shorts to ground or between coils. Frequent steering wheel rotation commonly causes this fatigue damage or long-term wear.
  • 2Short circuit in the driver airbag module (DAB) internal second-stage inflator igniter due to a manufacturing defect, long-term vibration causing the internal bridge wire to contact the housing, or internal corrosion after water ingress.
  • 3Airbag wiring harness chafing at the steering column, dashboard frame, or wiring channel edges damages the insulation and causes a short to ground, especially on vehicles with previous accident repairs or modifications.
  • 4Water ingress, oxidized or bent pins, or loose terminals at the front SRS connector (yellow waterproof connector) causing a short circuit. Common in vehicles driven through water or operated in high-humidity environments.
  • 5Internal detection circuit fault in the SRS control module (ACU) or damaged sampling resistor, causing a false short-circuit fault (actual external circuit resistance is normal)
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment and personal injury during repair.
  • 2
    Fault confirmation and freeze frame analysis: Connect the BYD VDS or a dedicated diagnostic tool to read the freeze frame data for DTC B17841A. Confirm whether the fault is Active or History, and record key information such as vehicle speed and collision signal status at the time of the fault.
  • 3
    Visual and connector inspection: Check the SRS wiring harness below the steering wheel and inside the dashboard for damage or crush marks. Check the yellow SRS connector (usually located below the steering wheel or behind the airbag module) for water ingress, corrosion, looseness, or bent pins.
  • 4
    Airbag module isolation check: Carefully disconnect the driver airbag module connector (usually a yellow 2-pin or 4-pin connector). Use a dedicated shorting bar or digital multimeter to measure the resistance between the stage 2 igniter terminals; the normal value is 1.8-3.2 Ω. Measure the resistance between each terminal and body ground; the value must be infinite (OL).
  • 5
    Clock spring (spiral cable) test: Disconnect the clock spring from the airbag module. Measure the harness resistance and insulation to ground at the lower side of the clock spring (towards the SRS ECU). While slowly turning the steering wheel from lock to lock, check for intermittent short circuits or sudden changes in resistance.
  • 6
    Harness continuity and insulation test: Disconnect the SRS control module (ACU) connector. Test the harness between the ECU and the airbag for shorts to ground or wire-to-wire shorts. Focus inspection on the sections routed along the steering column and instrument panel frame. If necessary, use a probe to check for internal harness breaks shorting to ground.
  • 7
    Component replacement cross-check: If the wiring harness tests normal, cross-check with a known-good clock spring or a dedicated airbag load simulator to confirm whether the fault is in the external circuit or internal to the SRS ECU (never measure an unknown airbag module directly with a multimeter set to resistance).
  • 8
    System repair and verification: After replacing the faulty component, fully engage all SRS connector locks (listen for two clicks). Reconnect the battery, clear the fault code, and perform three ignition cycle self-checks. Confirm B17841A does not reappear and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV clock spring internal wear causing short circuit

✓
The instrument cluster airbag warning light stays on. VDS reads active fault code B17841A. Disconnected the driver airbag module; the second stage igniter resistance measured normal at 2.1Ω. Further testing showed the clock spring's second stage igniter circuit resistance to ground drops to 0.3Ω when the steering wheel is at full right lock. Disassembled the clock spring and found the internal flat cable insulation worn at the winding center; copper foil contacting the metal housing caused an intermittent short. Replaced the OEM clock spring (part number must match the VIN). Fault resolved and system self-test passed.
BYD DTC AI Analysis

E2 model: Internal short circuit in airbag module igniter

✓
After driving through water, DTC B17841A set and would not clear. Clock spring wiring harness insulation checked good; found no shorts. Direct measurement between the driver airbag module Stage 2 igniter pin and metal housing read 0Ω, confirming internal seal failure in the airbag module and a short to ground between the igniter bridge wire and housing. Replaced the driver airbag assembly (includes gas generator and cushion—note Stage 1 and Stage 2 igniter pin definitions). Cleared the DTC and performed a simulated crash test; system functions normally.
BYD DTC AI Analysis

Dashboard wiring harness chafing caused intermittent SRS short circuit

✓
The BYD E3's airbag warning light came on intermittently when driving on rough roads. The scanner showed intermittent fault code B17841A. Disassembly revealed that a dashcam mounting screw had pierced the SRS harness corrugated tube on the instrument panel frame, causing the stage-2 airbag harness copper core to contact the metal frame. Repaired the insulation with high-temp insulation tape and fresh corrugated tube, rerouted the harness to avoid sharp metal edges. Fault eliminated.
BYD DTC AI Analysis

False positive fault in SRS ECU internal sampling circuit

✓
The vehicle had no collision history when DTC B17841A suddenly appeared. Replaced the clock spring and airbag module; fault persisted. Oscilloscope check of the SRS ECU igniter detection pulse waveform revealed internal sampling circuit reference voltage drift, causing the ECU to misjudge normal 2.0Ω resistance as 0Ω short. Replaced the airbag control module (ACU), recoded the vehicle configuration, and calibrated the crash sensors. The system returned to normal and the fault code did not reappear.
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.