AU
B179B-00

This DTC indicates the front passenger seat belt pretensioner Stage 2 squib circuit is shorted to vehicle power positive (B+) — Qin Plus

Safety System

This DTC indicates the front passenger seat belt pretensioner Stage 2 squib circuit is shorted to vehicle power positive (B+).

Modern vehicle seat belt pretensioners typically use a dual-stage ignition design: the first stage deploys during the initial collision phase to provide basic restraint, and the second stage deploys upon detecting a more severe collision to increase protective force.

A short to power indicates an abnormal high-potential path in the squib circuit, which may cause: 1) The pretensioner to deploy unintentionally in non-collision situations, causing personal injury and property damage; 2) The Airbag Control Unit (ACU) to detect abnormal circuit voltage and enter fail-safe mode, disabling the front passenger airbag and pretensioner functions; 3) Continuous short-circuit current to damage the internal ACU driver circuit or trigger fuse protection.

This constitutes a severe electrical fault in the passive safety system and requires immediate repair.

The B179B-00 fault code on the Qin Plus indicates a high-severity fault where the front passenger seat belt pretensioner Stage 2 squib circuit is shorted to battery power. This can disable safety restraint functions or risk unintended deployment. Common causes include damaged SRS wiring under the passenger seat or in the B-pillar, or an internal Airbag Control Unit driver fault. Visit an authorised dealer immediately for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Abrasion of the SRS wiring harness sleeve under the front passenger seat or inside the B-pillar causes the pretensioner drive wire to short to the power wire (constant power or ignition power).
  • 2Power MOSFET breakdown or driver chip failure in the Airbag Control Unit (ACU) internal ignition driver circuit, causing a continuous high-level output at the ignition terminal.
  • 3Frequent seat rail adjustment pinches and bends the pretensioner wiring harness secured under the seat, damaging the insulation and causing a short circuit to the chassis or power wire.
  • 4Short circuit between the internal igniter of the front passenger seat belt pretensioner and the metal housing, or water ingress or corrosion at the connector terminals causing a short circuit between the positive and negative terminals.
  • 5Vehicle wading, spilled liquids, or improper car washing causes water ingress into the pretensioner connector beneath the seat (typically located below the B-pillar or on the inboard side of the seat), creating an electrolytic conductive path between the terminals.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3-5 minutes for the SRS system energy storage capacitor to fully discharge. Wear an anti-static wrist strap. Do not use a standard multimeter to directly measure the ignition circuit (use a dedicated airbag resistor or diagnostic tool).
  • 2
    Visual inspection: Remove the front passenger lower B-pillar trim and seat (if necessary). Inspect the seat belt pretensioner wiring harness (wrapped in yellow corrugated conduit) for obvious wear, damaged insulation, or burn marks. Focus on harness mounting points and bends near the seat slide rail.
  • 3
    Circuit isolation check: Disconnect the connector between the ACU and the pretensioner. Use a digital multimeter (high-impedance mode) to measure the voltage from each terminal of the pretensioner-side connector to body ground (should be 0V). Measure the resistance from each terminal to the positive power supply (should be greater than 1MΩ) to check for a short circuit to power.
  • 4
    Pretensioner unit inspection: Measure the pretensioner unit resistance (normal value: approx. 1.5-2.5Ω; refer to the workshop manual for exact specifications). If the resistance is abnormally low or shows continuity, replace the pretensioner assembly.
  • 5
    Wiring harness repair: If the wiring harness is damaged, use specialized heat-shrink tubing or replace the entire SRS wiring harness. Do not simply wrap the harness with electrical tape. Verify the ground wire connection under the seat is secure to rule out a possible indirect short circuit.
  • 6
    Module-level verification: If the wiring harness and pretensioner are normal, inspect the ACU connector pins for deformation, push-out, or corrosion. If necessary, verify the ACU using the substitution method. Perform coding configuration after replacement.
  • 7
    System reset and test: Reconnect all connectors and turn on the power. Use the BYD VDS2000/3000 or Launch X431 diagnostic tool to clear the fault code. Perform the SRS system self-check and seat belt pretensioner function test. Confirm DTC B179B-00 does not return and the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Frequent seat adjustment caused wiring harness chafing and short circuit

✓
Model: 2018 BYD Qin EV450. Symptoms: Airbag warning light constantly illuminated on the instrument cluster. DTC B179B-00 stored. Diagnosis: Found the SRS wiring harness (yellow) beneath the front passenger seat rubbing against the metal seat rail edge when the seat was in its foremost position. The insulation had worn through, exposing the copper wiring that contacted the seat heater power cable (red), causing a short circuit. Repair: Replaced the dedicated SRS wiring harness between the floor harness and the pretensioner. Repositioned the harness clips and added abrasion-resistant sleeving to prevent pinching during full seat travel. Cleared the fault codes and road tested. Fault resolved.
BYD DTC AI Analysis

B-pillar pretensioner connector corroded from water ingress

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Vehicle: BYD Qin 100 2017 model. Symptoms: Airbag warning light on after driving through water; diagnostic tool showed code B179B-00. Diagnosis: Removed the front passenger side B-pillar lower trim and found the pretensioner connector (2-pin yellow plug) had obvious water stains and green corrosion. Insulation resistance between terminals dropped to approximately 200Ω, creating a soft short to power. Cause: Deteriorated door seal allowed rainwater to leak into the B-pillar cavity. Repair: Cleaned the connector with electronic cleaner, applied conductive grease after drying, replaced the waterproof sealing ring, and sealed around the connector with waterproof tape. Also replaced the slightly oxidised pretensioner terminals.
BYD DTC AI Analysis

Internal driver fault in airbag control module

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Model: 2017 BYD Qin 80. Symptoms: No collision history, but airbag warning light comes on intermittently. DTC B179B-00 appears sporadically. Diagnosis: Measured pretensioner harness resistance and insulation; both normal. Wiggled harness—fault did not appear. Disconnected pretensioner plug and measured at ACU side: found intermittent continuity (approx. 50-200 Ω) between ignition drive terminal and battery positive. Identified as poor thermal stability of ACU internal drive circuit or dry solder joint. Repair: Replaced airbag control module (ACU) and wrote vehicle configuration (VIN matching, sensor configuration, etc.). Fault eliminated.
BYD DTC AI Analysis

Front passenger pretensioner internal short circuit

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Vehicle: BYD Qin EV300 2017. Symptoms: SRS warning light comes on immediately at startup. DTC B179B-00 will not clear. Diagnosis: Disconnected the pretensioner connector. Resistance across the pretensioner terminals measured 0.3Ω (abnormally low; normal is ~2Ω). Continuity present between terminals and pretensioner metal housing. Internal short between igniter and housing. Repair: Replaced front passenger seatbelt assembly (including pretensioner). New component resistance: 2.1Ω. Cleared DTC after installation. System self-test passed. Probable cause: Insulation material defect from manufacturing or previous external impact.
BYD DTC AI Analysis

Power supply short from aftermarket seat heater installation

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Vehicle: 2018 BYD Qin EV450. Symptoms: B179B-00 DTC after adding seat ventilation/heating to the passenger seat. Diagnosis: The shop bundled the heating pad power feed (constant power) with the SRS pretensioner harness beneath the seat without insulation. Road vibration chafed through the power wire insulation, shorting it to the igniter wire inside the pretensioner harness. Repair: Restored factory harness routing, rerouted the retrofit circuits separately with an inline fuse, and protected them with OEM-spec corrugated tubing. Code cleared. Warning: Non-OEM electrical modifications are strictly prohibited near SRS harnesses.
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.