AU
B17351B

DTC B17351B indicates the SRS (Supplemental Restraint System) control unit detects a communication interruption or open electrical connection between the right second-row side airbag module (typically located on the right rear seat side or C-pillar) and the main control unit — Seal U

Safety System

DTC B17351B indicates the SRS (Supplemental Restraint System) control unit detects a communication interruption or open electrical connection between the right second-row side airbag module (typically located on the right rear seat side or C-pillar) and the main control unit.

Specifically, this open circuit fault indicates the airbag ignition circuit resistance falls outside the normal range (typically >10Ω or reading infinite).

This fault prevents the affected side airbag from deploying normally during a collision.

It may also deactivate the entire airbag system (entering fail-safe mode) and retain only the driver airbag function, severely compromising occupant side-impact protection.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Airbag wiring harness connector under the seat or inside the C-pillar trim panel is loose, disconnected, or has poor contact, especially near the adjustable seat slide rails where frequent adjustment loosens the connector.
  • 2Open circuit in the right middle-row side airbag assembly internal igniter, or module failure. Airbag module aging or an internal open circuit usually causes this fault.
  • 3Physical damage to the wiring harness, especially between the seat frame and vehicle body where long-term bending and pinching fractures the copper core (common in vehicles with frequent fore-and-aft seat adjustment).
  • 4Corroded, oxidized, or backed-out connector terminals causing increased terminal contact resistance due to vehicle wading, high-humidity environments, or liquid ingress during cleaning.
  • 5Internal detection circuit fault in the SRS control unit. Although rare, a damaged right-side airbag circuit detection port on the control unit also triggers this fault.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS or ED-400) to read the fault code, confirm whether B17351B is a current fault (Active) or a history fault (History), and record the freeze frame data.
  • 2
    Turn off the ignition, disconnect the negative battery terminal, and wait at least 90 seconds (to ensure the SRS capacitor fully discharges). Remove the right middle row seat or C-pillar trim panel, then locate the side airbag module connector (usually yellow or orange, with a shorting bar).
  • 3
    Visually inspect the connector to ensure it is fully seated and the shorting bar operates correctly. Check the terminals for corrosion, oxidation, or backed-out pins. Clean the terminals with electrical contact cleaner if necessary.
  • 4
    Disconnect the airbag module connector. Use a multimeter to measure continuity between the harness-side connector and the SRS control unit (<1Ω). Measure insulation resistance to ground and power (>10MΩ) to verify the harness has no open or short circuits.
  • 5
    Connect the airbag simulator (resistor, usually a dedicated 2-3Ω resistor) to the wiring harness connector. Reconnect the battery and turn the ignition switch ON. Use the diagnostic tool to clear the fault code and read the data stream. Confirm the system displays a normal resistance value (2-5Ω) and the fault code does not return.
  • 6
    If the simulator test passes, replace the right middle-row side airbag module assembly. If the fault persists, inspect and repair the wiring harness between the SRS control unit and the airbag, or replace the SRS control unit.
  • 7
    After completing the repair, reinstall all components and perform an SRS system self-check (normally, turning the ignition switch ON illuminates the airbag warning light for 6 seconds before it turns off). Perform a road test to confirm complete fault resolution.
Real-World Cases
BYD DTC AI Analysis

Right rear side airbag connector detached on E2 rideshare vehicle

✓
2019 BYD E2 ride-hailing vehicle with 85,000 km. Airbag warning light on. Read DTC B17351B. Inspection found frequent removal of the right rear seat for cargo had completely detached the side airbag connector. Reconnected the connector and secured the wiring harness with cable ties. Cleared the fault code; system returned to normal.
BYD DTC AI Analysis

Flood-damaged Qin EV: corroded airbag terminals

✓
A 2019 Qin EV had water enter the cabin from a blocked sunroof drain tube, pooling in the right C-pillar. After repairs, DTC B17351B appeared. Disassembling the right second-row side airbag connector revealed severely oxidised, green terminals. Cleaned the terminals with electronic cleaner and applied conductive protectant. Resistance measurements returned to normal, clearing the fault.
BYD DTC AI Analysis

E3 seat wiring harness broke due to prolonged flexing

✓
The owner of a 2020 E3 with 120,000 km reported the airbag warning light illuminating intermittently. The diagnostic tool showed intermittent fault code B17351B. Inspection found the wiring harness beneath the right rear seat had fractured copper cores with intact insulation at the seat rail mounting point, caused by repeated seat adjustments over time (hidden fault). Stripping back the harness revealed the internal conductor was 80% broken. Resoldering the joint and reinforcing the protection resolved the fault.
BYD DTC AI Analysis

Did not clear fault after replacing airbag module.

✓
Replaced the right second-row side airbag module on an E2 during accident repair, but DTC B17351B persisted after installation. The new module connector seated properly, yet the scan tool showed infinite resistance. Found that pulling during removal of the old airbag had damaged the wiring harness, causing the terminals to back out inside the connector. Repairing the terminals cleared the fault. Avoid yanking the wiring harness when servicing airbag systems.
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.