AU
B176712

This DTC indicates the Airbag Control Unit (ACU) detects a short to positive (+B) in the RH front side curtain airbag ignition circuit — Qin Plus

Safety System

This DTC indicates the Airbag Control Unit (ACU) detects a short to positive (+B) in the RH front side curtain airbag ignition circuit.

Under normal conditions, the airbag ignition circuit remains in a high-resistance state (infinite) or exhibits a specific resistance (typically >2Ω) only during circuit diagnostics.

When the ACU detects continuous battery voltage (12V) or a resistance near 0Ω on this circuit, it logs a short to power.

This hardwire short circuit causes the following: 1) Airbag fails to deploy during a collision (power supply clamps the circuit); 2) Unintended airbag deployment in extreme cases (if the ACU drive circuit and the shorted point form a complete circuit); 3) The ACU enters fail-safe mode, cuts power to this circuit, illuminates the SRS warning light, and degrades overall airbag system functionality.

The B176712 fault code on the Qin Plus indicates a short to battery positive in the right front side curtain airbag ignition circuit. This is a high-severity SRS fault that can prevent correct airbag deployment or, in rare cases, cause unintended deployment. Common causes include worn harness insulation near the A-pillar or roof rail, and water ingress or corrosion at the airbag connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Worn harness insulation: The right front curtain airbag harness routes along the A-pillar and roof side rail. Long-term vibration or door seal aging causes the harness to rub against body metal edges. Damaged insulation allows contact with power wires (such as reading light or sunroof motor power wires).
  • 2Connector water ingress and oxidation: An aged seal on the airbag connector (usually yellow) located in the headliner or below the A-pillar allows water from car washes or sunroof leaks to enter. This forms an electrolyte bridge between the pins, short-circuiting the ignition pin to the power supply pin.
  • 3Airbag Control Unit (ACU) internal fault: ACU internal ignition drive transistor breakdown or filter capacitor short circuit causes continuous high-level output on this channel.
  • 4Damage from non-professional modifications: Fixing screws piercing the airbag wiring harness when installing a dash cam or roof ambient lighting, or mistakenly connecting the airbag circuit as a ground or power wire.
  • 5Airbag module internal short circuit: The bridge wire inside the curtain airbag inflator igniter shorts to the housing, or moisture in the ignition powder causes an abnormal drop in resistance.
What To Do
  • 1
    Safety Preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to ensure the ACU backup power supply discharges completely. Wear an anti-static wrist strap. Never use a multimeter resistance setting to directly measure the airbag inflator.
  • 2
    Visual inspection: Remove the right A-pillar trim, rear section of the headliner, and right rear C-pillar trim. Inspect the curtain airbag wiring harness (yellow corrugated conduit) for signs of abrasion, crushing, or puncture. Focus inspection on the rubber grommets where the harness passes through openings.
  • 3
    Connector diagnosis: Disconnect the connector between the ACU and the right front side curtain airbag. Set a multimeter to the voltage setting and measure the airbag-side wiring harness voltage to ground. A 12V reading confirms the wiring harness is shorted to power. Measure the resistance between the ACU-side pins and power to verify the ACU has no internal short circuit.
  • 4
    Sectional isolation: Use a short-circuit detector or sectional disconnection method to divide the wiring harness into three sections: ACU to A-pillar, A-pillar to C-pillar, and C-pillar to airbag. Measure insulation resistance to power section by section to locate the exact short circuit position.
  • 5
    Component replacement verification: If the wiring harness is normal, connect a dedicated airbag simulator (2Ω) to the ACU in place of the curtain airbag. Clear the fault code and power on for a self-check. If the fault code disappears, replace the airbag module. If the fault code remains, replace the ACU.
  • 6
    Repair verification: After repairing the damaged wiring harness (use double-layer heat shrink tubing for insulation; do not simply wrap with electrical tape) or replacing the faulty component, reconnect all connectors and restore power. Use the diagnostic tool to perform an 'SRS system self-test' and 'crash sensor calibration'. Verify B176712 does not return and the SRS warning lamp turns off.
Real-World Cases
BYD DTC AI Analysis

BYD E2: Worn A-pillar wiring harness causing intermittent short circuit

✓
2019 E2, 80,000 km. SRS light intermittent, DTC B176712 intermittent. Found airbag harness inside right front A-pillar trim rubbing against sheet metal burr, insulation worn through exposing copper. Contacted reading lamp power wire over bumps. Repaired harness with heat-shrink tubing, rerouted and secured wiring, added rubber protective sleeve. Fault resolved.
BYD DTC AI Analysis

BYD Qin EV sunroof leak caused connector short circuit

✓
2019 Qin EV. SRS warning light stayed on after heavy rain with DTC B176712. The sunroof drain tube had detached, allowing water into the right-side headliner. The curtain airbag connector above the C-pillar had oxidized pins; a water film was conducting between the power and airbag igniter pins. Cleaned the connector pins, applied conductive grease, reattached the drain tube and replaced the connector seal. Issue resolved.
BYD DTC AI Analysis

E3: Wiring harness incorrectly connected during dash cam installation

✓
2020 model E3. Owner fitted a dashcam themselves and, when tapping power, mistakenly identified the airbag circuit in the roof harness as the ACC feed, causing a short-to-power in the right front side curtain airbag circuit. Inspection found the airbag harness inside the A-pillar had been stripped and connected to a power tap. Restored the original harness and replaced the damaged airbag harness assembly (reliability insufficient if repaired). Fault cleared.
BYD DTC AI Analysis

ACU internal driver circuit fault

✓
2019 BYD Qin EV repeatedly triggered DTC B176712. Replaced the airbag and wiring harness; fault persisted. Monitored ACU output with a scope and found 12V present on this channel immediately at power-on. Determined the ACU internal ignition driver chip had shorted. Replaced the airbag control unit (located beneath the center console), performed coding and sensor calibration. Normal operation restored.
BYD DTC AI Analysis

Curtain airbag inflator internal short circuit

✓
BYD E2. Following flood damage, DTC B176712 set. Removed the right front side curtain airbag and measured 0.3Ω between the gas generator ignition terminals (normal >2Ω). Internal moisture caused a short. Replaced the curtain airbag module (requires headliner removal) and inspected the other airbag modules on the same side. Confirmed no water ingress before reassembly. 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.