AU
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 — Atto 8

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 Atto 8 indicates a short in the driver-side front airbag Stage 2 firing circuit, with resistance detected at 0 ohms. This is a medium-severity SRS fault that can disable the airbag and reduce driver protection in a crash. Common causes include a shorted clock spring or an internal short in the airbag inflator. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Broken internal wire shorting to ground or interlayer short circuit in 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 second-stage squib, or inflator body failure (manufacturing defect or internal short circuit due to prolonged moisture).
  • 3Airbag wiring harness connector (usually located beneath the steering wheel or near the main crossmember) has water ingress, backed-out terminals, or damaged insulation causing a short to body ground.
  • 4Improper repair procedures (such as removing the airbag without disconnecting the battery negative 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 ohm reading.
What To Do
  • 1
    Safe power-off: Turn off the ignition switch, 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 a dedicated diagnostic tool to read the DTC. Verify B1784 is a current fault code (Active) and cannot be cleared. Record the freeze frame data.
  • 3
    Visual inspection: Check the clock spring connector below the steering wheel and the airbag wiring harness corrugated tube for damage, water ingress, or burn marks. Check the pins for oxidation or backing out.
  • 4
    Resistance measurement: Remove the driver airbag module using the special tool. Disconnect the connector, then measure the resistance from both terminals of the secondary ignition circuit to ground (should be infinite). Measure the circuit resistance (normal: 2.0-3.0 Ω). A 0 Ω reading 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 consider the airbag module last). Never measure the airbag igniter directly with a multimeter.
  • 7
    System reset: Reconnect all connectors (ensure locking tabs engage fully), switch on the power, clear the fault code using the diagnostic tool, and perform 'Collision Output Check' and 'Configuration Information Write'.
  • 8
    Function check: Perform SRS system self-diagnosis and confirm B1784 does not return. Read the data stream to verify Stage 2 airbag resistance is within the normal range (2.0±0.5Ω). 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

✓
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

✓
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 Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.