AU
B174A-00

This fault code indicates the measured resistance of the left rear side airbag (Side Airbag, Left Rear) firing circuit is 0 ohms, confirming a short circuit — Qin Plus

Safety System

This fault code indicates the measured resistance of the left rear side airbag (Side Airbag, Left Rear) firing circuit is 0 ohms, confirming a short circuit.

In the BYD SRS (Supplemental Restraint System), normal airbag squib resistance ranges from 1.5 to 3.5 ohms.

A 0-ohm reading indicates a direct short circuit between the firing circuit power wire (Squib+) and ground wire (Squib-), or the airbag module detects abnormally low internal resistance.

This condition causes the SRS control unit to identify an unintended deployment risk, illuminate the airbag warning light, and disable the left rear side airbag.

Unlike a "resistance too high/open circuit" fault (infinite resistance), damaged wiring insulation, connector water ingress, or mechanical damage typically causes short circuits.

Inspect the circuit immediately to prevent potential overheating.

4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Water ingress, moisture, or oxidation at the left rear seat side airbag connector (usually located under the seat or inside the C-pillar trim) causes a short circuit between the metal terminals.
  • 2The rear seat adjustment mechanism, seat belt mechanism, or a foreign object chafed the airbag wiring harness under the seat or inside the B/C-pillar trim panel. Damaged insulation caused the positive and negative conductors to contact and short circuit.
  • 3Rear passengers stepping on the side of the seat, compression from heavy objects, or fixing clips piercing the wiring harness during seat modifications (leather retrimming or installing seat covers), causing an internal short circuit in the harness.
  • 4Internal short circuit in the left rear side airbag module igniter coil (very rare; usually exhibits characteristic airbag internal short-circuit resistance)
  • 5SRS control unit (ACU) internal detection circuit fault or bent connector pin causing a short circuit, resulting in a false 0 Ω resistance reading.
What To Do
  • 1
    Use the BYD VDS2000/2100 diagnostic tool to read the fault code, confirm B174A-00 is 'Active', and record the voltage and ambient temperature from the freeze frame data.
  • 2
    Perform the safety procedure: 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).
  • 3
    Remove the left rear seat assembly (usually requires removing 4 retaining bolts and lifting the seat) and locate the side airbag module connector (yellow connector with short-circuit protection tab).
  • 4
    Disconnect the airbag connector. Use a digital multimeter (minimum 10MΩ input impedance) to measure the resistance between the two terminals of the airbag assembly. The normal value is 1.5-3.5Ω. If the reading is 0-0.5Ω, replace the airbag. If the reading is normal, the fault is in the wiring harness.
  • 5
    Measure the wiring harness side: Measure the resistance between each of the two connector terminals and body ground (should be infinite), and the resistance between the two terminals (should be infinite). Continuity indicates a short circuit.
  • 6
    Carefully inspect the airbag wiring harness outer sheath along the routing path (typically along the seat rail, B-pillar lower trim panel, and floor harness channel). Focus on interference points at the seat movement mechanism and harness retaining clips. Repair any damage (use heat-shrink tubing or replace the harness section).
  • 7
    Check inside the connector for metal debris, liquid, or deformed terminals. Clean with electrical contact cleaner and verify the shorting bar functions normally.
  • 8
    Restore all connections, reconnect the battery, and clear the fault code. Perform the 'ignition cycle test' (ON-OFF 3 times) and 'SRS system self-test'. Verify the fault code does not return and the instrument cluster airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Water ingress under the left rear seat caused the connector to short-circuit.

✓
A 2018 Qin EV450 came in with the airbag warning light on. Inspection found damp carpet under the left rear seat, likely from a spilled drink or water leaking past a poor window seal. Removing the seat revealed obvious water marks inside the yellow airbag connector. The terminals had micro-shorting from electrolyte corrosion, with resistance measuring 0.3Ω. The technician cleaned the connector with electrical contact cleaner, dried it, and the resistance returned to normal. They also traced the water ingress to a blocked left rear window drainage channel; clearing the drain holes resolved the fault.
BYD DTC AI Analysis

Aftermarket genuine leather seats pierced airbag wiring harness.

✓
2017 BYD Qin 100. After the owner had the seats reupholstered in leather at a custom trim shop, fault code B174A-00 appeared. Inspection found the trimmer used excessively long staples or clips to secure the leather, piercing the left rear seat side airbag harness (inside the seat back side trim) and shorting the positive and negative wires. Replaced the damaged harness section from the airbag connector to the floor harness connection point, re-routed the wiring properly, and secured it with dedicated harness clips to avoid contact with the seat frame. Fault resolved.
BYD DTC AI Analysis

Worn wiring harness at rear seat folding mechanism

✓
A Qin EV300 with 80,000 km developed intermittent fault codes. Inspection revealed that at the pivot of the left rear seat folding mechanism (40/60 split), the airbag wiring harness had been flexing repeatedly as the seat folded and unfolded. This caused fatigue damage to the insulation, exposing the copper core, which then contacted the seat's metal frame and created a short circuit. Released slack in the wiring harness, fitted protective corrugated tubing at the flex point, repositioned the harness mounting points to clear moving parts, and wrapped the area with felt tape to prevent squeaks.
BYD DTC AI Analysis

Loose connector; metal debris caused short circuit

✓
2017 Qin 80. After driving over rough roads, the airbag warning light illuminated. Found the airbag connector under the left rear seat not fully locked (possibly not fully seated during a previous repair). A small metal circlip had fallen into the connector (likely from the seat installation process), causing a short between the terminals. Removed the foreign object, confirmed the CPA (connector position assurance) was intact, reseated the connector with an audible click, and cleared the DTCs. Fault resolved.
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.