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) — Qin Plus

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.

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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Clock spring (spiral cable) internal conductor breaks and shorts to ground or between windings. Fatigue damage from frequent steering wheel rotation or long-term wear commonly causes this fault.
  • 2Short circuit in the stage 2 igniter generator inside the driver airbag module (DAB). Possible causes include a manufacturing defect, long-term vibration causing the internal bridge wire to contact the housing, or internal corrosion after water ingress.
  • 3The airbag wiring harness chafes against the steering column, instrument panel frame, or wiring duct edges, damaging the insulation and causing a short to ground, especially on vehicles with previous accident repairs or modifications.
  • 4Water ingress into the front SRS connector (yellow waterproof connector), oxidized or bent pins, or loose terminals causing a short circuit; common in vehicles driven through deep water or operated in high-humidity environments.
  • 5SRS control module (ACU) internal detection circuit fault or damaged sampling resistor causes a false short-circuit fault (actual external circuit resistance is normal).
What To Do
  • 1
    Safe power-off: 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 current (Active) or historical (History). Record key information from the time of the fault, such as vehicle speed and collision signal status.
  • 3
    Visual and connector inspection: Check the SRS wiring harness below the steering wheel and inside the instrument panel 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 test: 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 second-stage igniter pins. The normal value is 1.8-3.2 Ω. Measure the resistance between each pin and body ground; the value should 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 resistance changes.
  • 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 shorts between wires. Focus inspection on the sections routed past the steering column and instrument panel frame. If necessary, use a probe to check for internal harness breaks causing a ground fault.
  • 7
    Component replacement cross-check: If the wiring harness tests normal, use a known-good clock spring or dedicated airbag load simulator to cross-check and confirm whether the fault is in the external circuit or internal to the SRS ECU (never use a multimeter in resistance mode to measure an unknown airbag module directly).
  • 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, perform a self-check over three ignition cycles, and confirm B17841A does not return 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 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.