AU
B173611

DTC B173611 indicates the SRS (Supplemental Restraint System) control unit detects an abnormal short to body ground in the firing circuit of the right second-row side airbag module (typically located on the side of the right second-row seat or the lower B-pillar) — Seal U

Safety System

DTC B173611 indicates the SRS (Supplemental Restraint System) control unit detects an abnormal short to body ground in the firing circuit of the right second-row side airbag module (typically located on the side of the right second-row seat or the lower B-pillar).

The airbag module contains an electric squib (igniter) controlled by the airbag ECU, with a normal resistance between 1.5 and 2.5 Ω.

The diagnostic system logs a short to ground when the circuit-to-ground resistance drops below the threshold (typically under 1 Ω or a specific calibrated value).

This fault produces the following consequences: 1) The side airbag fails to deploy during a collision, resulting in a loss of side-impact protection; 2) In extreme cases, short-circuit current triggers unintended airbag deployment, causing occupant injury; 3) The SRS enters fail-safe mode, disabling the entire vehicle airbag system.

This constitutes a highest-severity electrical safety fault requiring immediate repair.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Airbag module internal igniter coil short circuit: Moisture ingress, aging, or manufacturing defects damage the internal coil insulation of the squib inside the right middle-row side airbag module, causing direct continuity to the module's metal housing (ground).
  • 2Physical damage to the wiring harness: Frequent seat adjustment, foreign object pinching, or vehicle vibration wears the harness insulation near the seat rail, inside the B-pillar trim panel, or under the floor, causing the signal wire to contact the vehicle body metal directly.
  • 3Connector water ingress and corrosion: Vehicle wading, a blocked sunroof drain hose, or interior cleaning allows moisture to enter the right middle-row side airbag connector, causing terminal oxidation and creating a short-to-ground path.
  • 4Internal SRS ECU fault: Airbag control unit internal monitoring circuit malfunction falsely reports a short-to-ground fault (relatively uncommon; confirm after ruling out wiring faults).
  • 5Improper repair work: During seat removal and installation, interior trim modification, or audio system modification, tools pierce the wiring harness, or unsecured retaining clips cause the wiring harness to rub against the vehicle body and short circuit.
What To Do
  • 1
    Safety pre-operation: Turn the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds (to fully discharge the SRS capacitor and prevent accidental airbag deployment).
  • 2
    Initial visual inspection: Remove the right middle-row seat side trim panel or the lower B-pillar trim panel. Check the airbag module for external damage, the wiring harness for obvious damage or burn marks, and the connector for looseness or water ingress.
  • 3
    Circuit isolation diagnosis: Disconnect the SRS control unit connector. Use a multimeter to measure the resistance between the right middle-row side airbag pin (refer to the wiring diagram, typically the B1736 channel) and body ground. Normal resistance is greater than 1MΩ (open circuit). Resistance less than 1Ω confirms a short to ground.
  • 4
    Segmented fault isolation: Disconnect the wiring harness at the airbag module connector. Measure the resistance to ground on the harness side and the module side separately. If the module side is shorted, replace the airbag module. If the harness side is shorted, inspect along the wiring route, focusing on seat rail chafing points and detached harness retaining clips.
  • 5
    Repair and verification: Repair the damaged wiring harness (using waterproof insulating tape and corrugated conduit) or replace the faulty airbag module. Reconnect all connectors and ensure the retaining clips lock into place. Connect the battery, clear the fault code using a VDS or X431 diagnostic tool, and perform the SRS system self-check procedure. Verify B173611 does not return and the airbag warning light turns off.
  • 6
    Function check: Perform static and dynamic tests, including simulated vehicle start-up and a bumpy road driving test, to verify the fault does not recur.
Real-World Cases
BYD DTC AI Analysis

Worn seat rail wiring harness caused a short to ground

✓
Vehicle: 2019 BYD E2, 60,000 km. The customer reported an intermittent airbag warning light on the instrument cluster. Using VDS, the technician retrieved DTC B173611. After removing the right-hand rear seat, the technician found the seat track adjustment mechanism had worn through the airbag wiring harness corrugated tubing over time, allowing the copper core to directly contact the seat metal frame and short to ground. Repair: Cut out the damaged harness section, soldered in extension wires, insulated the splices with double-layer heat shrink tubing, and rerouted the wiring away from the seat track travel path. Fault resolved.
Original source ↗
BYD DTC AI Analysis

After wading, water entered the connector, causing corrosion and a short circuit.

✓
Vehicle: 2019 BYD Qin EV. Warning light illuminated after driving through water in heavy rain. Scan tool displayed code B173611 and could not clear it. Inspection found damp carpet beneath the right rear seat. Removing the side airbag connector revealed obvious water stains and green copper corrosion inside. Cause: aged door seal allowed rainwater to seep in and pool at the floor wiring harness connector. Fix: cleaned connector oxides thoroughly, sprayed electronic cleaner and dried, applied conductive grease, replaced the waterproof seal, and cleared the fault codes. System returned to normal.
Original source ↗
BYD DTC AI Analysis

Connector not reconnected after accident repair caused short circuit

✓
Vehicle: 2020 BYD E3. After a repair shop replaced the B-pillar trim following a right rear door accident, the instrument cluster displayed an airbag warning. Fault code B173611 was stored. Inspection revealed the technician had not fully seated the airbag connector when installing the right rear side airbag module (locking tab unengaged). The plug tilted, allowing the signal pin to contact the body metal and short to earth. Rectification: Reconnected the airbag module connector correctly, ensuring the locking tab clicked into place. Secured the wiring harness with cable ties to eliminate strain. Cleared the DTC and completed airbag system calibration.
Original source ↗
Other Seal U 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.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.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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.