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B1784

DTC B1784 indicates the driver-side front airbag Stage 2 firing circuit resistance is 0 ohms, signifying a short to ground or an internal short circuit in the gas generator secondary firing circuit — Qin Plus

Safety System

DTC B1784 indicates the driver-side front airbag Stage 2 firing circuit resistance is 0 ohms, signifying a short to ground or an internal short circuit in the gas generator secondary firing circuit.

Modern airbag systems use a staged deployment strategy: Stage 1 deploys during moderate collisions, while Stage 2 deploys during severe collisions based on parameters such as seat position and seat belt usage to enhance protection.

A resistance of 0 ohms means the SRS ECU detects circuit impedance below the threshold (typically less than 1.0Ω).

This triggers the safety lockout mechanism and disables the airbag.

This fault severely compromises driver protection during a collision and requires immediate repair.

The B1784 fault code on the Qin Plus indicates a Stage 2 driver front airbag firing circuit short, with resistance detected at 0 ohms. Severity is medium because the SRS may disable the airbag, reducing crash protection. Common causes include a shorted clockspring/spiral cable or an internal short in the driver airbag module. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Broken internal wire shorted to ground or interlayer short circuit within the airbag clock spring (spiral cable/clockspring), causing the Stage 2 ignition circuit to short to ground.
  • 2Internal short circuit in the driver airbag module secondary squib, or inflator body fault (manufacturing defect or prolonged moisture causing an internal short circuit)
  • 3Airbag wiring harness connector (usually located under the steering wheel or near the main crossmember): water ingress, terminal pin back-out, or damaged insulation causing a short to body ground.
  • 4Improper repair procedures (such as removing the airbag without disconnecting the negative battery terminal) causing accidental deployment or wiring damage resulting in a short circuit.
  • 5Internal fault in the SRS control unit detection circuit (such as a burnt sampling resistor or damaged A/D converter) causing a false 0 Ω resistance reading.
What To Do
  • 1
    Safe power-off: Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Connect the VDS or dedicated diagnostic tool to read the DTC. Confirm B1784 is a current fault code (Active) and fails to clear. Record the freeze frame data.
  • 3
    Visual inspection: Check the clock spring connector below the steering wheel and the airbag wiring harness corrugated conduit for damage, water ingress, or burn marks. Check for oxidized or backed-out pins.
  • 4
    Resistance measurement: Remove the driver airbag module using the special tool. Disconnect the connector. Measure the resistance to ground at both terminals of the stage 2 ignition circuit (expected: infinite). Measure the circuit resistance (normal: 2.0-3.0 Ω). 0 Ω confirms a short circuit.
  • 5
    Sectional isolation: Disconnect the clock spring from the wiring harness. Measure resistance on the airbag side, clock spring side, and body wiring harness side separately to pinpoint whether the short circuit is in the airbag unit, clock spring, or main wiring harness.
  • 6
    Component replacement: Replace the faulty component based on the diagnostic results (replace the clock spring first, then check the wiring harness, and finally consider the airbag module). Never directly measure the airbag igniter with a multimeter.
  • 7
    System reset: Reconnect all connectors (verify locking tabs are fully engaged), turn on the power, clear the fault code using the diagnostic tool, and perform 'Collision Output Check' and 'Configuration Information Write'.
  • 8
    Function verification: Run the SRS system self-diagnosis to confirm B1784 does not recur. Read the data stream to verify the Stage 2 airbag resistance is within the normal range (2.0 ± 0.5 Ω). Perform a road test to confirm.
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM driver airbag second stage circuit short to ground (B1784)

✓
Symptom: Instrument panel airbag warning light stayed on. VDS scan showed B1784 (driver second stage front airbag resistance 0 Ω). Diagnosis: With the battery disconnected, inspection found pin 3 of the clock spring connector G10 under the steering wheel had backed out and touched the metal bracket, shorting the second stage squib circuit to ground. Airbag module measured 2.3 Ω (normal); harness side read 0 Ω to ground. Resolution: Re-seated the backed-out pin, re-routed and secured the harness to clear the steering column, and installed a protective sleeve to prevent chafing. Cleared the fault code; resistance returned to 2.1 Ω and the warning light went out.
Original source ↗
BYD DTC AI Analysis

BYD Han EV airbag system intermittently sets B1784

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Symptoms: When driving over speed bumps or rough roads, the instrument cluster intermittently displayed 'Check Airbag System', with fault code B1784. Diagnostic process: Found the fault consistently reproduced at a specific steering wheel angle (left turn approximately 15°). Disassembly revealed the clock spring's internal ribbon cable rubbing against the housing at full lock, wearing through the insulation and causing intermittent shorts to ground. Resistance measured normal at rest, but dropped to 0Ω when turning the steering wheel. Solution: Replaced the clock spring assembly, re-centered the installation, and calibrated the steering angle sensor to the SRS system.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro reports B1784 fault with zero resistance after repair

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Symptoms: After the dealership replaced the steering column, the vehicle immediately threw a B1784 on startup. Secondary airbag resistance read 0Ω. Diagnosis: The technician skipped standard procedure. During steering wheel installation, the steering column mounting bolt crushed the airbag harness, grounding the secondary igniter line directly to the chassis. Disassembly revealed torn harness insulation with copper wires contacting the frame. Fix: Replaced the entire airbag harness, rerouted the wiring to maintain clearance from metal edges, and reinforced protection with insulation tape. Post-repair insulation resistance measured >10MΩ. Fault cleared.
Original source ↗
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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.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 Qin Plus →Qin Plus 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.