AU
B1784-00

This fault code indicates a low resistance or short circuit in the driver-side front airbag Stage 2 inflator circuit — Seal 6 EV

Safety System

This fault code indicates a low resistance or short circuit in the driver-side front airbag Stage 2 inflator circuit.

The SRS control unit detects a circuit resistance of 0 ohms (normal range: 2.0-3.0 ohms).

Dual-stage airbag systems deploy based on collision severity: Stage 1 provides partial inflation, and Stage 2 provides full deployment for maximum protection.

A 0-ohm resistance typically indicates a short circuit in the inflator itself, the internal wiring of the clock spring (spiral cable), or a wiring harness short to ground.

This fault causes the SRS system to identify a risk of unintended Stage 2 deployment.

Consequently, the system illuminates the airbag warning light and may disable the entire driver-side front airbag, severely compromising occupant protection during a collision.

The B1784-00 fault code on the Seal 6 EV indicates low resistance or a short circuit in the driver-side front airbag Stage 2 inflator circuit. Severity is medium because the airbag warning light may come on and the driver airbag may be disabled. Common causes include a faulty steering wheel clock spring or a shorted second-stage airbag inflator. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Steering wheel clock spring (spiral cable) internal winding short circuit or breakage causing a short to ground. This is a common steering system fault in the BYD Qin series.
  • 2Short circuit in driver airbag assembly internal second-stage igniter (airbag assembly fault, possibly due to aging or manufacturing defects)
  • 3Long-term steering wear damaged the airbag wiring harness insulation near the steering column, causing a short circuit to the steering wheel metal frame.
  • 4SRS control unit (ACU) internal drive circuit fault causing a false code (rule out wiring faults before confirming)
  • 5After vehicle wading or deep interior cleaning, water ingress into the airbag connector (especially the gray connector under the steering wheel) causes a short circuit between terminals.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to completely discharge the SRS backup power supply and prevent accidental airbag deployment.
  • 2
    Initial inspection: Remove the access covers on both sides of the steering wheel, disconnect the airbag module connector, and check the connector terminals for green oxidation, water stains, or deformation.
  • 3
    Measure the airbag module: Use a digital multimeter to measure the resistance between the second-stage squib pins on the airbag module side. Normal resistance is 2.0-3.0 Ω. If the resistance is close to 0 Ω, replace the driver airbag assembly.
  • 4
    Inspect the clock spring: Disconnect the wiring harness connector below the clock spring and measure the resistance to ground on the lower side (towards the SRS ECU). If the resistance is not infinite, inspect the wiring harness. Measure continuity between the corresponding upper and lower terminals of the clock spring. If abnormal, replace the clock spring assembly.
  • 5
    Harness inspection: Carefully inspect the yellow SRS wiring harness sleeve between the steering column and the steering wheel for wear or signs of crushing. Specifically check for pinched wires at the steering column tube retaining clip.
  • 6
    System reset: After repair, reconnect all connectors (listen for the locking click). Connect the battery. Clear the fault code using VDS2000 or a Launch diagnostic tool. Perform the 'SRS system self-check' and 'igniter circuit test'.
  • 7
    Function check: Perform a simulated crash test (use the diagnostic tool to perform an actuator activation test without deployment). Confirm B1784-00 does not recur and all steering wheel functions (horn, multi-function buttons) operate normally.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV450 clock spring internal short circuit causing B1784-00

✓
2018 Qin EV450, 62,000 km. Airbag warning light on. DTCs B1784-00 and B1783-00 (first-stage resistance abnormal). Disassembly found the clock spring damaged during a previous steering wheel modification. Measuring continuity from top to bottom showed 0.3Ω between second-stage circuit pins (normal: continuity with measurable resistance). Replaced with OEM clock spring (part number: BYD-3658310-XX). Second-stage circuit resistance restored to 2.4Ω. Cleared codes; system normal.
BYD DTC AI Analysis

Qin 100 airbag connector corroded and short-circuited after water wading

✓
2017 BYD Qin 100. After driving through water, instrument cluster displayed "Check SRS System". Scanning revealed active DTC B1784-00. Removed driver airbag; connector (grey 2-pin) had significant water staining and green corrosion. Cleaned and dried terminals, but still measured 0Ω — igniter internally short-circuited. Replaced driver airbag module (new mounting bolts required) and applied anti-corrosion treatment to wiring harness connector. Fault resolved.
BYD DTC AI Analysis

Aftermarket steering wheel caused wiring harness to chafe and short circuit.

✓
A 2017 BYD Qin 80 showed an airbag warning light after the owner installed a third-party steering wheel cover and modifications. Diagnostics revealed intermittent DTC B1784-00. Inspection found the SRS wiring harness had not been secured correctly during the modification; it was rubbing against a metal bracket inside the steering column, wearing through the insulation and causing an intermittent short to ground. Repaired the damaged wiring with high-temperature tape and corrugated tubing, then re-routed and secured the harness to factory specifications with adequate slack for steering wheel rotation. The fault did not recur.
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.