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B174111

DTC B174111 indicates a short to ground in the Left Rear Side Airbag ignition circuit — Qin Plus

Safety System

DTC B174111 indicates a short to ground in the Left Rear Side Airbag ignition circuit.

In the SRS (Supplemental Restraint System), this means the wiring between the Airbag Control Unit (ACU) and the left rear side airbag module (typically the low-side drive wire or high-side power wire) has an abnormal electrical connection to vehicle ground (GND).

This drops the circuit resistance abnormally, typically below 1-2 ohms.

This fault causes the ACU to detect a short-circuit risk in the airbag circuit.

To prevent accidental deployment or insufficient ignition energy, the system disables the airbag and illuminates the instrument cluster airbag warning light.

The left rear side airbag typically mounts inside the C-pillar trim panel or on the side of the rear seat.

The wiring harness routes through crush-prone areas, such as the sill trim panel and seat rails, making mechanical damage a frequent cause of this fault.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Wiring harness mechanical damage: A loose or detached wiring harness retaining clip inside the left rear door sill trim panel causes the harness to rub against the seat slide rail or sharp body edges over time. This damages the insulation and causes a short circuit to the metal body.
  • 2Improper seat modification/repair: During rear seat removal/installation or leather trimming, fixing screws or clips pierce the side airbag wiring harness, causing the wire core to short to ground.
  • 3Connector water ingress and corrosion: Vehicle wading or poor floor sealing allows water to enter the airbag connector below the left B/C pillar (usually a yellow waterproof plug), causing electrolytic corrosion between the terminals and a short to ground.
  • 4Airbag module internal short circuit: Internal insulation failure of the clock spring or squib inside the airbag assembly causes the ignition circuit to short to ground.
  • 5SRS control unit internal fault: A damaged airbag driver transistor or monitoring circuit inside the ACU falsely reports a short to ground (external wiring is normal).
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation and data recording: Use a VDS2000 or Launch X431 diagnostic tool to read complete fault codes and freeze frame data. Record parameters such as vehicle speed, temperature, and voltage at the time of the fault. Confirm B174111 is a current fault (Present), not a history fault.
  • 3
    Initial visual inspection: Remove the left rear door sill trim, lower C-pillar trim, and seat. Inspect the wiring harness for wear, cuts, pinch marks, or water stains, focusing on the harness routing at the seat mounting bolts.
  • 4
    Circuit sectional isolation test: Disconnect the ACU connector (usually under the center armrest box or front bulkhead) and the left rear side airbag module connector. Use a multimeter to measure the airbag circuit resistance to ground. Normal resistance is infinity (>10kΩ). Resistance less than 1Ω confirms a short to ground.
  • 5
    Locating the short circuit: Inspect the wiring harness using the "split-half method". Strip back the harness at the midpoint of the main loom to inspect or measure. Gradually narrow the search area until you locate the damaged point. Common fault locations include the corrugated conduit of the door sill wiring harness or the transition area under the seat.
  • 6
    Component-level test: If the external wiring harness tests normal (good insulation to ground), directly measure the resistance to ground at the two pins on the airbag module. It should show no continuity. If continuity exists, replace the left rear side airbag assembly. (Note: Do not measure airbag resistance while energized.)
  • 7
    Repair and replacement: Repair the damaged wiring harness (use waterproof heat-shrink tubing or replace the entire harness). Secure the harness in place, route it correctly, and maintain sufficient clearance from the seat slide rail. If the connector is corroded, replace the connector terminals. If the airbag module or ACU fails, replace the corresponding component.
  • 8
    System verification: Reconnect all connectors and the battery. Clear the fault code and perform three ignition cycles (OFF-ON-ACC). Verify the SRS warning light turns off normally. Use the diagnostic tool to perform 'SRS system self-test' and 'crash sensor calibration' (if applicable). Verify B174111 does not return and the system status displays 'normal'.
Real-World Cases
BYD DTC AI Analysis

An aftermarket rear seat modification on a Qin Pro DM pinched the wiring harness, causing a short circuit.

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A 2018 Qin Pro DM logged fault code B174111. The owner reported recently having leather seat upholstery fitted at an automotive accessory market. The mechanic found a self-tapping screw beneath the left rear seat mounting bracket had pierced the wiring harness corrugated tubing, causing the black/yellow wire (ignition negative) in the airbag circuit to make direct contact with the screw (body earth). Removed the screw, repaired and re-secured the harness. Fault cleared.
BYD DTC AI Analysis

Corroded door sill wiring harness connector on water-wading vehicle

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2019 BYD Qin Pro (petrol). Airbag warning light remained on after wading through water during a typhoon. Diagnostic scanner retrieved DTC B174111. Removed the left rear sill trim panel and found the airbag harness connector below the B-pillar (yellow 2-pin plug) had obvious water staining and verdigris; terminal-to-ground resistance measured 0.3Ω. Cleaned and dried the terminals, applied conductive anti-corrosion paste, reconnected the harness, and cleared the fault code. The fault has not recurred.
BYD DTC AI Analysis

C-pillar interior trim panel improperly installed, chafed wiring harness

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After the accident repairs, the dealer replaced the left rear C-pillar trim panel. A week later, the SRS light came on. A scan revealed active fault code B174111. When the dealer removed the trim, they found the trim clip had pressed against the airbag harness during installation, damaging the insulation and exposing copper wires that contacted the vehicle body. They replaced about 30 cm of the damaged harness and rerouted the wiring away from the clip, which fixed the problem.
BYD DTC AI Analysis

Internal short circuit in left rear side airbag module

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2019 BYD Qin Pro DM. No accident history or modifications. SRS warning light came on suddenly. Inspected external wiring harness insulation – good. Measured continuity between ACU and airbag harness – normal, no short to ground. However, resistance between the two pins of the airbag module itself and ground measured only 0.8Ω. Diagnosed internal ignition coil insulation failure in the airbag. Replaced left rear side airbag assembly (required removing C-pillar trim). Fault cleared.
BYD DTC AI Analysis

SRS control unit internal driver circuit fault

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Rare case: vehicle required multiple return repairs. Despite replacing the wiring harness and airbag module, DTC B174111 persisted. An oscilloscope check of the ACU output waveform showed the channel driver transistor had shorted to ground, continuously outputting a short-to-ground signal regardless of external load. Replaced the airbag control unit (ACU) and performed coding (requires writing the vehicle VIN and crash sensor configuration parameters). This completely resolved the issue.
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.