AU
B17301A

DTC B17301A indicates the Supplemental Restraint System (SRS) detected a resistance of 0 ohms in the left middle-row (second-row left-side) side airbag module firing circuit, indicating a hard short circuit — Seal U

Safety System

DTC B17301A indicates the Supplemental Restraint System (SRS) detected a resistance of 0 ohms in the left middle-row (second-row left-side) side airbag module firing circuit, indicating a hard short circuit.

Normal airbag squib resistance is between 2.0 Ω and 4.0 Ω.

A resistance of 0 ohms indicates current passes directly through the circuit without load.

Possible causes include an internal short circuit in the airbag ignition wire, a wiring harness short to ground, a short circuit between connector terminals, or a fault in the SRS control unit (ACU) internal detection circuit.

Upon detecting this fault, the ACU immediately illuminates the airbag warning lamp and disables the left middle-row side airbag to prevent accidental deployment from the short circuit.

Consequently, the airbag will fail to deploy during a collision, posing a severe safety hazard.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Short circuit in the left middle row side airbag module internal igniter: Moisture, aging, overload, or manufacturing defects break down the insulation between the positive and negative terminals of the internal igniter wire, creating a short circuit.
  • 2Seat wiring harness worn and shorted to ground: During middle-row seat forward and backward sliding or backrest angle adjustment, the airbag wiring harness rubs against the seat frame, slide rail, or spring, damaging the insulation and causing a short to vehicle body ground.
  • 3Connector fault: Water ingress, bent pins, detached terminals, foreign objects, or oxidation in the yellow airbag-specific connector (usually equipped with a shorting bar) located under the seat or inside the C-pillar trim, causing a short circuit between terminals.
  • 4SRS control unit (ACU) internal fault: A damaged ACU crash sensor interface circuit or ignition driver circuit triggers a false short circuit fault (actual external wiring is normal).
  • 5Improper modification or repair: Retaining clips or cable ties crush or pierce the airbag wiring harness during seat removal and installation, reupholstering in leather, or installing seat cushions or floor mats, causing a short circuit in the harness.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor and prevent accidental airbag deployment and personal injury.
  • 2
    Fault Confirmation: Use a VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B17301A is an active fault, not a historical fault. Record the resistance value and ambient temperature from the freeze frame data.
  • 3
    Visual inspection: Check the side of the left middle-row seat (second-row left side) for signs of impact, water damage, or modification. Check the airbag marking location (usually on the side of the backrest or C-pillar).
  • 4
    Connector inspection: Remove the seat side trim panel or lower C-pillar trim panel. Locate the yellow dedicated airbag connector (usually containing a shorting bar/shorting spring) and check for looseness, water ingress, oxidation, or bent or deformed pins.
  • 5
    Resistance measurement: Disconnect the airbag module connector. Use a multimeter to measure the resistance on the airbag module side (standard value: 2.0-4.0Ω). If the reading is 0Ω or close to 0Ω, the airbag module has an internal short circuit. Replace the module.
  • 6
    Wiring harness insulation check: If the airbag module resistance is normal, measure the resistance to ground on the wiring harness side (should be infinite). If continuity exists (0Ω), the wiring harness has a short to ground. Trace the circuit to troubleshoot, focusing on wear points at the seat slide rails, hinges, and mounting brackets.
  • 7
    Shorting bar function test: Inspect the connector shorting bar for binding or deformation. Verify the shorting bar reliably shorts the circuit when disconnecting the plug (to prevent accidental deployment from static electricity) and springs fully open when connecting the plug.
  • 8
    Repair and replacement: Repair the damaged wiring harness (insulate with double-layer heat-shrink tubing or replace the entire harness) or replace the faulty airbag module. Note: Record the old and new part numbers when replacing the airbag module. Some models require coding configuration.
  • 9
    System reset: Reconnect all connectors, connect the battery, clear the fault code using the diagnostic tool, and perform the SRS system self-diagnosis (including circuit resistance monitoring and system check).
  • 10
    Function check: Verify the instrument cluster airbag warning lamp turns off after the self-check (approximately 6 seconds). Read the data stream to confirm the left middle-row side airbag resistance returns to the normal range of 2.0-4.0Ω. Adjust the seat forward and backward to verify no interference.
Real-World Cases
BYD DTC AI Analysis

Worn wiring harness on middle row seat caused short circuit in Song MAX

✓
Model: 2019 BYD Song MAX, 32,000 km. Issue: Airbag warning light stayed on constantly. VDS scan retrieved DTC B17301A (left second-row side airbag resistance 0 Ω). Repair: Removed the left second-row seat. Found the airbag wiring harness sheath chafed through at the seat rail, allowing the copper wires to touch the seat frame and short to ground. Repaired the harness with heat-shrink tubing and re-secured the routing. Cleared the DTCs – fault resolved.
Original source ↗
BYD DTC AI Analysis

Qin EV left middle row side airbag module internal short circuit

✓
Vehicle: 2020 BYD Qin EV. Symptom: Airbag warning light on, DTC B17301A. Disconnected the left centre-row seat side airbag connector and directly measured resistance between the airbag module pins: 0.2 Ω (normal 2–4 Ω). This indicated an internal short in the igniter. Replaced the left centre-row side airbag module. Resistance returned to 3.1 Ω and the fault cleared. Repair cost around 1200 yuan.
Original source ↗
BYD DTC AI Analysis

Song DM: Oxidised connector under seat causing short circuit

✓
Model: 2018 BYD Song DM. Symptom: Airbag warning light stays on after startup. VDS read DTC B17301A. Diagnostic steps: Inspected the yellow airbag connector beneath the left middle-row seat. Found green oxidation and slightly deformed pins inside, causing a micro-short between terminals. Cleaned the connector terminals with electronic contact cleaner, straightened the pins, and applied conductive paste. Cleared the fault codes and monitored the vehicle for one week — no recurrence.
Original source ↗
BYD DTC AI Analysis

Aftermarket seat modification crushed airbag wiring harness on Han EV

✓
Vehicle: 2021 BYD Han EV, 8 months from new. The airbag warning light came on suddenly. The dealership diagnosed DTC B17301A. A subsequent workshop inspection found that the owner's seat cover retaining clips had crushed the left rear side airbag harness, causing a short between the positive and negative wires. The workshop re-wrapped the harness and adjusted the clip positions. Total repair cost: 50 yuan.
Original source ↗
BYD DTC AI Analysis

e5 450 wiring harness improperly secured, chafed and shorted

✓
Vehicle: 2017 BYD e5 450. The airbag warning light on the instrument cluster stayed on. The diagnostic scanner read DTC B17301A (left centre row side airbag circuit resistance 0 ohms). Removed the left centre row seat and found the airbag wiring harness unsecured at the seat rail. Long-term friction wore through the insulation, causing a short to ground. Repaired the damaged harness and re-routed and secured the wiring as per the workshop manual to prevent contact with moving parts.
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.