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B172C11

DTC B172C11 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance path from the left second-row side airbag ignition circuit (usually the left B-pillar side airbag or seat side airbag) to body ground (GND), with a resistance typically <1Ω — Qin Plus

Safety System

DTC B172C11 indicates the SRS (Supplemental Restraint System) detected an abnormally low-resistance path from the left second-row side airbag ignition circuit (usually the left B-pillar side airbag or seat side airbag) to body ground (GND), with a resistance typically <1Ω.

The airbag system ignition circuit features a dual-circuit redundant design (high side and low side).

Under normal conditions, resistance to ground should be >100kΩ.

Upon detecting a short to ground, the SRS ECU identifies a risk of unintended deployment or failure to deploy.

The ECU immediately illuminates the airbag fault warning lamp and disables that side airbag and any linked restraint systems (such as the seatbelt pretensioner).

This is a hard short circuit, not an intermittent fault.

Repair immediately for occupant safety.

The B172C11 fault code on the Qin Plus indicates a high-severity short to ground in the left second-row side airbag ignition circuit. This can disable the side airbag and related restraint systems, so it needs immediate attention. Common causes include damaged wiring in the left B-pillar trim or a pinched under-seat airbag harness. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Wiring harness wear inside the left B-pillar trim panel: Prolonged driving on rough roads or repeated removal and installation of the B-pillar trim panel causes the side airbag wiring harness (usually wrapped in yellow corrugated conduit) to rub against sharp metal body edges. This damages the insulation layer, causing the copper core to contact the chassis ground directly.
  • 2Under-seat harness pinched and shorted: On models equipped with seat side airbags, dynamic movement between the seat fore-aft adjustment mechanism and the floor harness fixing point causes the seat slide rail to pinch or wear through the harness sleeve, resulting in a short to ground.
  • 3Connector water ingress and corrosion: An aging left front door seal or window leak allows water into the airbag wiring harness connector at the A/B-pillar junction (usually inside the sill trim panel). This forms an electrolytic conductive path between the pins, causing a short to ground.
  • 4Airbag module internal short circuit: Manufacturing defects or long-term high-temperature aging damage the igniter bridge wire insulation inside the side airbag inflator, causing the bridge wire to short to the metal housing. Replace the entire airbag module.
  • 5SRS ECU internal driver circuit fault: The high-side or low-side drive MOSFET inside the ECU breaks down, shorting the output terminal to ground. This condition usually triggers simultaneous short circuit faults in multiple airbag circuits.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds (to fully discharge the SRS capacitor). Wear an anti-static wrist strap, and prepare a dedicated diagnostic tool (such as BYD VDS 3000 or Launch X-431) and a multimeter.
  • 2
    Freeze frame analysis: Connect the diagnostic tool to read the DTC freeze frame data. Record parameters such as vehicle speed, temperature, and voltage at the time of the fault. Determine whether it is a continuous fault (current DTC) or a history fault.
  • 3
    Visual inspection: Remove the left B-pillar lower trim panel, sill trim panel, and seat (if applicable). Check the yellow airbag wiring harness for obvious damage, crushing, water stains, or corrosion. Focus on the contact points between the wiring harness and the body metal.
  • 4
    Circuit measurement: Disconnect the connector between the SRS ECU and the side airbag module. Use a multimeter to measure the resistance from the harness-side connector pins (usually 2 pins, high side and low side) to body ground. The normal reading is infinite resistance (OL). A reading of 0-5 Ω confirms a harness short to ground.
  • 5
    Sectional isolation: Use the half-split method to inspect the wiring harness section by section. Measure at the airbag module connector. If the short circuit disappears, the wiring harness is faulty. If the short circuit persists, check the ECU side. For the seat side airbag, check the mating connector between the seat wiring harness and the floor wiring harness.
  • 6
    Repair or replace: If the wiring harness is damaged, repair it using heat-shrink tubing or insulating tape, and re-secure the harness to prevent further chafing; if the connector is corroded, clean or replace the connector; if the airbag module has an internal short circuit, you must replace it with a genuine airbag module (do not repair).
  • 7
    System verification: Reconnect all connectors, connect the battery, and use the diagnostic tool to clear the fault code. Perform the SRS system self-check (normally, the self-check lamp illuminates for 6 seconds after turning the ignition switch to ON, then turns off). Perform static and dynamic road tests to confirm B172C11 does not reappear and the airbag warning lamp operates normally.
Real-World Cases
BYD DTC AI Analysis

E2: Left B-pillar wiring harness chafing caused intermittent short circuit

✓
A 2019 BYD E2 with 30,000 km on the odometer developed an intermittent airbag warning light on the instrument cluster. The scan tool read current fault code B172C11. Removed the left B-pillar trim and found the side airbag wiring harness had chafed through at the retaining clip due to prolonged vibration, exposing the copper core and contacting the body shell. Wrapped the damaged section with insulating tape, rerouted the harness to increase slack, and replaced the retaining clip to eliminate sharp edge contact. Followed up for one month after the repair with no recurrence.
BYD DTC AI Analysis

Qin EV seat rail crushed side airbag wiring harness

✓
2020 BYD Qin EV. Customer reported the airbag warning light illuminated after adjusting the seat position. Technicians found the left front seat side airbag harness (floor harness section) pinched under the seat slide rail mounting bolt, with damaged insulation causing a short to ground. Root cause: The dealer did not follow the standard harness routing when previously replacing the carpet. Repair: Replaced the damaged harness section (from main harness to seat connector), rerouted it along the floor harness channel per the workshop manual, secured it with dedicated harness clips, and ensured no interference throughout the full seat travel range.
BYD DTC AI Analysis

Water leak from E3 left front door caused connector corrosion.

✓
A 2020 E3 showed fault code B172C11 after the rainy season. We found green copper corrosion inside the airbag wiring harness connector (C-03) located within the left A-pillar lower sill trim. Pin 3 (low side drive) showed continuity with the connector housing. We traced the leak to a perished left front door seal that let rainwater seep in, run down the B-pillar, and pool at the connector. We replaced the damaged connector (including terminals), dried the affected harness bundle, fitted a new left front door seal, applied waterproof silicone grease to the connector, and properly seated the waterproof plug.
BYD DTC AI Analysis

Side airbag module internal short circuit false alarm

✓
2019 BYD Qin EV. After accident repairs, replaced the left second-row side airbag. After installation, DTC B172C11 logged. Checked wiring harness ground insulation — normal, resistance >10 MΩ. Disconnected the airbag module and measured 0.3 Ω between the igniter pin and module casing, confirming an internal manufacturing defect in the new module causing a short to ground. Fitted another genuine airbag module, fault cleared. Tip: Protect airbag modules from static electricity and mechanical shock during transport and storage. Before installation, measure igniter resistance with a multimeter (normal: 2–3 Ω, infinite to ground).
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.