AU
B174B-00

This DTC indicates the firing circuit resistance of the left rear side airbag (typically integrated into the left rear door C-pillar trim panel or the side of the left rear seat backrest) falls below the SRS control module threshold (normal range 2 — Qin Plus

Safety System

This DTC indicates the firing circuit resistance of the left rear side airbag (typically integrated into the left rear door C-pillar trim panel or the side of the left rear seat backrest) falls below the SRS control module threshold (normal range 2.0-3.0Ω; fault threshold typically <1.0Ω or near 0Ω).

Low resistance indicates an abnormal low-resistance path in the circuit.

Causes include a short to ground, damaged wiring harness insulation, shorted connector pins, or an internal short in the airbag inflator bridge wire.

This fault forces the SRS system into a degraded mode and illuminates the airbag warning light.

During a collision, the affected airbag may fail to deploy (as the control module detects a short and disables the firing circuit) or, in extreme cases, deploy unintentionally.

The B174B-00 fault code on the Qin Plus indicates low resistance in the left rear side airbag firing circuit, putting the SRS system in degraded mode and turning on the airbag warning light. Severity is medium, as the airbag may not deploy correctly or could deploy unexpectedly in rare cases. Common causes include water ingress or damaged wiring/connectors. Visit an authorised dealer for inspection and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Water ingress and oxidation at the left rear door sill or C-pillar wiring harness connector: Driving through water, car washing, or poor sealing forms a conductive water film between the connector pins, creating parallel resistance.
  • 2Wiring harness mechanical damage: Improper rear seat removal/installation or door sill trim installation causes the seat rail to pinch the wiring harness and damage the insulation, resulting in a short to body ground.
  • 3Airbag module internal fault: Igniter bridge wire short circuit or damp propellant causes an abnormal resistance drop.
  • 4Poor plug contact: Backed-out or loose pins increase the effective contact area or cause abnormal bridging (resistance appears low, but contact is abnormal).
  • 5SRS ECU internal detection circuit fault: Abnormal control module internal sampling resistor or ADC circuit causes incorrect resistance reading.
What To Do
  • 1
    Safe power-down: Disconnect the 12V battery negative terminal and wait at least 3-5 minutes to completely discharge the SRS energy storage capacitor and prevent accidental deployment.
  • 2
    Inspection procedure: Remove the left rear C-pillar trim panel and door sill trim panel. Check the connection status of the white/yellow side airbag connector (usually marked 'Side Airbag').
  • 3
    Initial measurement: Use a high-precision multimeter (with seat belt resistance function) to measure the resistance between the airbag connector terminals. Normal resistance is 2-3Ω. If <1Ω, disconnect the connector and measure the harness-side resistance to ground.
  • 4
    Harness continuity check: Measure harness continuity and insulation from the airbag connector to the SRS ECU (usually located under the center console or in the front compartment). Inspect the sill harness bends for chafed insulation and shorts to ground.
  • 5
    Component isolation test: Use a dedicated 2-3Ω airbag simulator in place of the actual airbag. If the fault code changes to "resistance too high" or disappears, this confirms a short circuit in the airbag unit. Replace the airbag unit.
  • 6
    Repair procedure: If water is present, clean the connector with electrical contact cleaner, blow dry, then apply conductive paste. If the wiring harness is damaged, repair the insulation with heat-shrink tubing and re-secure the routing.
  • 7
    Replacement and matching: After replacing the faulty airbag or wiring harness, use VDS2000 or Launch X431 to perform 'Airbag System Configuration' (some models require online programming to match the VIN).
  • 8
    Verify clearance: Clear the DTC. Cycle the ignition switch to perform a self-check. Verify DTC B174B-00 does not return and the instrument cluster fault indicator turns off. Read the data stream to verify the resistance is 2.0-3.0 Ω.
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV450 left rear seat side airbag connector water ingress short circuit

✓
Symptoms: After driving through water, the airbag warning light stayed on. VDS detected active fault code B174B-00. Diagnosis: Removed and inspected the left rear sill trim panel. The side airbag harness connector showed obvious water ingress, with green copper corrosion between the pins. Resistance between pins measured only 0.4Ω (short circuit condition). Solution: Cleaned the connector with anhydrous ethanol and blow-dried it. After drying, harness-to-ground insulation tested normal. Reconnected the connector, applied waterproof silicone grease, and cleared the fault code. Circuit resistance returned to 2.4Ω.
Original source ↗
BYD DTC AI Analysis

BYD Qin 100 rear seat wiring harness wear causing low resistance

✓
Symptoms: Dashboard airbag warning light illuminates intermittently, particularly over rough surfaces. Diagnosis: DTC B174B-00 stored as intermittent fault. Removed left C-pillar trim and found side airbag wiring harness chafing against seat mounting bracket. Damaged insulation caused intermittent short to ground; resistance to ground fluctuated between 0.5-5MΩ. Solution: Repaired damaged wiring with heat shrink tubing and insulating tape, re-secured harness to original retaining clip positions, added corrugated tubing protection. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV300 airbag module internal short circuit

✓
Symptoms: Airbag warning light stays on continuously; DTC B174B-00 will not clear. Diagnosis: Disconnected the left rear side airbag connector. Resistance across the airbag unit pins measured only 0.6Ω (normal: 2–3Ω), indicating an internal short in the airbag igniter. Harness side resistance to ground measured >10MΩ, normal. Resolution: Replaced the left rear side airbag module (seat backrest removal required). Performed SRS system matching using VDS. After clearing the fault code, resistance reads 2.8Ω, normal.
Original source ↗
BYD DTC AI Analysis

BYD Qin 80: software false alarm and intermittent wiring harness connection

✓
Symptoms: 3-month-old vehicle logged DTC B174B-00. No accident or water submersion history. Diagnosis: Visual inspection of the wiring harness showed no abnormalities. Found slightly backed-out airbag connector pins, causing unstable contact resistance (intermittent low values). The SRS ECU had outdated software. Solution: Re-seated the backed-out pins to ensure full engagement. Updated the SRS control module software to the latest version (optimised resistance sampling algorithm). The fault has not recurred.
Original source ↗
BYD DTC AI Analysis

BYD Qin EV450 seat connector not fully seated after seat removal and refit

✓
Symptom: The owner reported the airbag warning light illuminated after the left rear seat was reupholstered. Diagnosis: Retrieved DTC B174B-00. Inspection revealed the side airbag connector was not fully locked; the internal shorting bar had made unintended contact, causing circuit resistance to drop abnormally to 0.9 ohms. Solution: Reinserted and secured the airbag connector, confirmed the locking tab engaged (audible click), cleared the DTC, and road tested to confirm normal system operation.
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.