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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 — Seal 6 EV

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 Seal 6 EV indicates a medium-severity SRS fault where the right middle-row side airbag igniter circuit shows 0 Ω resistance, usually meaning a short circuit. Common causes include an internal airbag igniter short or damaged seat wiring harness insulation from movement or chafing. Because this can prevent airbag deployment, the recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Airbag module internal igniter short circuit: Manufacturing defects, aging, or previous electrostatic discharge causes the igniter resistance wire to melt or short-circuit.
  • 2Seat wiring harness mechanical damage: The right second-row side airbag wiring harness routes through the seat frame or moves with seat adjustment. Long-term chafing damages the insulation, causing the core wire to short to ground.
  • 3Connector fault: Bent or backed-out terminals inside the yellow dedicated airbag connector, or short circuit between pins due to wading or cleaning fluid ingress.
  • 4SRS control unit internal fault: ACU internal detection circuit damaged, triggering a false 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: Switch off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to ensure the SRS capacitor fully discharges.
  • 2
    Fault confirmation: Use the dedicated diagnostic tool to read freeze frame data, record the vehicle status when the fault occurred, and confirm whether it is a current or historical fault.
  • 3
    Disconnect and measure: Remove the right middle-row seat side trim panel. Locate and disconnect the yellow airbag connector. Measure the resistance at the airbag module side using a digital multimeter (Normal: 2-5 Ω. If 0 Ω, replace the airbag module).
  • 4
    Harness continuity test: Measure the resistance to ground on the harness side (should be >1MΩ). Inspect the harness for wear at the seat rails and hinges, focusing 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 and 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 Seal 6 EV 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.B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.