AU
B174C

DTC B174C indicates the SRS (Supplemental Restraint System) detects the inflator resistance of the left rear side airbag (usually located inside the left rear C-pillar trim panel or on the side of the left rear seat) exceeds the system-calibrated threshold (typically above 3 — Seal 6 EV

Safety System

DTC B174C indicates the SRS (Supplemental Restraint System) detects the inflator resistance of the left rear side airbag (usually located inside the left rear C-pillar trim panel or on the side of the left rear seat) exceeds the system-calibrated threshold (typically above 3.0Ω; normal range is 1.5Ω-3.0Ω).

This fault indicates a high-resistance condition or open circuit in the airbag inflator circuit.

Inflator aging, poor wiring harness contact, or a broken wire can cause this condition.

This fault prevents the airbag from deploying correctly during a side-impact collision and continuously illuminates the dashboard airbag warning light (SRS light).

The system enters fail-safe mode, and some models may limit the seat belt pretensioner function.

The B174C fault code on the Seal 6 EV indicates high resistance or an open circuit in the left rear side airbag inflator circuit. Severity is medium because the airbag may not deploy correctly in a side impact and the SRS warning light stays on. Common causes include a loose or corroded connector, damaged wiring, or an aging airbag module. 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
  • 1Loose connection, terminal back-out, or terminal oxidation/corrosion at the left rear C-pillar airbag connector causing increased contact resistance.
  • 2Moisture ingress and aging of the igniter charge in the left rear side airbag module, or an open circuit in the squib coil, causing abnormally high resistance.
  • 3Long-term bending and chafing of the wiring harness at the rear seat folding mechanism or C-pillar trim panel edge causes internal wire breakage or shielding layer damage.
  • 4Moisture seeps into the airbag connector during vehicle wading or washing (especially due to poor sealing at the bottom of the C-pillar), causing gradual terminal oxidation.
  • 5SRS control module internal sampling resistor or A/D conversion circuit fault, causing a false high resistance reading (intermittent fault)
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal. Wait at least 3 minutes to discharge the residual charge in the SRS capacitor to prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use the BYD dedicated diagnostic tool (VDS3000) to read the DTC and confirm B174C is a current fault (Active), not a history fault (History).
  • 3
    Visual inspection: Remove the left rear C-pillar trim panel and check the connection status of the airbag module orange connector. Confirm there are no backed-out pins, loose connections, or obvious signs of water ingress.
  • 4
    Resistance measurement: Disconnect the airbag connector. Use a digital multimeter (accuracy 0.1 Ω or better) to measure the resistance directly between the airbag-side connector terminals. Normal resistance is 2.0 ± 0.5 Ω. A reading of OL (open circuit) or >5 Ω indicates a faulty airbag unit.
  • 5
    Harness inspection: If airbag resistance is normal, measure end-to-end harness continuity (SRS module to airbag connector). Check the harness at the seat hinge and C-pillar pass-through for high-resistance points (>1Ω is abnormal).
  • 6
    Simulation test: Connect a dedicated airbag simulator (2Ω resistor) to the circuit in place of the actual airbag. If the fault clears after power-on, the airbag unit is faulty. If the fault persists, inspect and repair the wiring harness or SRS module.
  • 7
    Repair/Replace: Replace the faulty airbag or repair the wiring harness (insulate with double-layer heat-shrink tubing after soldering). Rewrap with waterproof tape and ensure the connector locking tab is fully engaged.
  • 8
    System reset: Reinstall all components, connect the battery, use the diagnostic tool to clear fault codes, perform the SRS system self-check (Ignition Check), and verify the warning light turns off and the system has no current faults.
Real-World Cases
BYD DTC AI Analysis

Worn left rear C-pillar wiring harness caused B174C fault in BYD Tang DM

✓
The SRS warning light on the instrument panel stayed on. Scan tool showed active fault code B174C. Removed the left rear C-pillar trim and found the side airbag wiring harness rubbing against the edge of the C-pillar sheet metal hole. The insulation wore through, 90% of the copper strands broke, and only a few strands remained connected, causing intermittent resistance readings. Repair: Cut out the damaged section. Soldered in new 0.5mm² high-temperature fluoroplastic wire (overlap ≥20mm). Insulated with double-layer heat-shrink tubing. Rerouted the harness away from sharp sheet metal edges. Fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro Left Rear Side Airbag Connector Oxidation Case

✓
After three years of use, the vehicle developed an intermittent B174C fault with the SRS light illuminating in damp weather. Inspection found green copper corrosion on the terminals inside the left rear seat side airbag connector (beneath the seat backrest), caused by water ingress during car washing that did not dry. Contact resistance between the terminals measured 12Ω. Resolution: Cleaned the terminals with electronic cleaner, applied conductive protective grease, replaced the connector housing with a waterproof type, and re-crimped the terminals. The fault has not recurred.
Original source ↗
BYD DTC AI Analysis

BYD Han EV airbag igniter aging high-resistance fault

✓
Vehicle under collision repair (left rear side impact). After replacing the left rear quarter panel and C-pillar trim, the SRS warning light set DTC B174C. The replacement salvage airbag resistance measured 6.8 Ω (normal: 2.3 Ω). Long-term storage moisture caused chemical degradation inside the igniter. Installed a new left rear side airbag (part no. SA2E-62766-00), performed module configuration programming and system calibration. Resistance returned to normal 2.1 Ω, fault cleared.
Original source ↗
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.