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B173A1A

DTC 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 — Qin Plus

Safety System

DTC 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.

The B173A1A fault code on the Qin Plus indicates a short circuit in the right middle-row side airbag igniter circuit, with resistance measuring 0 Ω instead of the normal 2.0–5.0 Ω. This is a medium-severity SRS fault that can disable proper airbag deployment and keep the warning light on. Common causes include a faulty airbag igniter or damaged seat wiring harness. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Airbag module internal igniter short circuit: Manufacturing defects, aging, or previous electrostatic discharge caused the igniter resistance wire to blow or short circuit.
  • 2Seat wiring harness mechanical damage: The right middle row side airbag wiring harness typically routes through the seat frame or moves during seat adjustment. Prolonged friction damages the insulation, causing the core wire to short to ground.
  • 3Connector fault: Bent or backed-out internal terminals in the yellow dedicated airbag connector, or water or cleaning fluid ingress causing a short circuit between pins.
  • 4SRS control unit internal fault: Damaged ACU internal detection circuit falsely reports a short circuit fault (confirm after ruling out external wiring).
  • 5Improper modification or repair: Failing to secure the wiring harness during seat removal and installation, or piercing the airbag wiring harness when installing seat covers.
What To Do
  • 1
    Safe power down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 90 seconds for the SRS capacitor to fully discharge.
  • 2
    Fault confirmation: Use the dedicated diagnostic tool to read freeze frame data, record the vehicle status when the fault occurred, and determine whether the fault is current or historical.
  • 3
    Disconnect and measure: Remove the right middle-row seat side trim panel. Locate and disconnect the yellow airbag connector. Use a digital multimeter to measure the resistance at the airbag module side (normal: 2-5 Ω; if 0 Ω, replace the airbag module).
  • 4
    Harness continuity test: Measure the harness-side resistance to ground (>1 MΩ). Inspect the harness for wear at the seat rails and hinges. Focus on the flexible harness section that moves with the seat.
  • 5
    Connector inspection: Inspect terminals for bending or corrosion, and measure for short circuits between connector terminals. Clean or replace the connector if necessary.
  • 6
    Repair verification: After repairing or replacing the faulty component, reconnect all connectors, reconnect the battery, use the diagnostic tool to clear the fault code, and perform a 'system self-check' (complete 3 ignition cycles).
  • 7
    Final confirmation: Confirm the SRS warning lamp is off. Use the diagnostic tool to read the data stream and confirm the airbag resistance value has returned to the normal range.
Real-World Cases
BYD DTC AI Analysis

Worn seat rails caused a wiring harness short circuit.

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Vehicle: 2019 Qin EV Symptom: SRS light always on, fault code B173A1A. Diagnosis: Removed right second-row seat. Found side airbag harness clip had detached from the seat fore-aft adjustment rail. The rail trapped the harness, chafed through the insulation, and caused a short to earth. Measured resistance to earth: 0.3 ohms. Solution: Replaced damaged harness section. Rerouted and secured the harness, then added abrasion-resistant sleeving. Fault cleared.
BYD DTC AI Analysis

Corrosion in airbag connector due to water ingress

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Model: E3 2020. Symptoms: SRS warning light on after wading through water, storing DTC B173A1A. Diagnosis: Inspected the right middle-row side airbag connector (under the seat) and found obvious water stains and verdigris corrosion inside. Decreased insulation resistance between terminals caused a short circuit. Water level likely exceeded the floor wiring harness height when the vehicle waded through water. Resolution: Replaced the airbag harness connector (including terminals), cleaned the airbag module pins, and dried the entire vehicle wiring harness. Fault cleared.
BYD DTC AI Analysis

Airbag module internal igniter fault

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Model: E2 2019. Symptoms: After accident repairs and replacement of the airbag, the SRS warning light remained illuminated with DTC B173A1A. Diagnosis: Disconnected the airbag module connector and measured 0Ω across the module terminals (normal reading is 2-3Ω), confirming the new aftermarket airbag module had a manufacturing defect in the internal igniter causing a short circuit. Testing on the wiring harness side showed normal resistance (infinite to ground). Fix: Replaced the genuine right middle row side airbag module, recoded the system, and restored normal operation.
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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.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.