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B17171B

DTC B17171B indicates the SRS (Supplemental Restraint System) control module detects an open circuit in the left knee airbag (Driver Knee Airbag) igniter circuit — Seal 6 EV

Safety System

DTC B17171B indicates the SRS (Supplemental Restraint System) control module detects an open circuit in the left knee airbag (Driver Knee Airbag) igniter circuit.

The resistance value falls outside the normal range (normal: approx. 2-3Ω; open circuit: >10Ω or infinite).

This fault indicates a physical break in the wiring or connector between the airbag ECU and the left knee airbag assembly, or an internal open circuit within the airbag igniter itself.

The knee airbag protects the driver's lower limbs from dashboard intrusion during a frontal collision.

This fault prevents the airbag from deploying during a crash and may trigger the SRS secondary protection mechanism (e.g., disabling the associated airbag group), posing a severe safety hazard.

In the BYD diagnostic protocol, the '1B' suffix specifically denotes an 'open circuit/high resistance' condition.

The B17171B fault code on the Seal 6 EV indicates an open or high-resistance circuit in the driver’s left knee airbag igniter. This is a medium-severity SRS fault because the knee airbag may not deploy in a crash. Common causes include a loose or disconnected yellow SRS connector under the dash, damaged wiring, or an internal airbag igniter fault. The recommended fix is to visit an authorised dealer. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal 6 EV
  • 1Knee airbag wiring harness connector loose or disconnected: The dedicated yellow SRS connector located under the instrument panel near the steering column may develop poor contact due to water intrusion, vehicle modifications, or failure to fully seat the connector after repairs.
  • 2Airbag igniter internal open circuit: Broken or degraded igniter coil inside the knee airbag assembly, usually accompanied by damage to the airbag module itself. This typically results from failure to replace the airbag after a collision or the airbag reaching the end of its service life (vehicles over 10 years old).
  • 3Physical damage to the wiring harness: Pedal operation, floor mat compression, or accident repairs pull the under-dash wiring harness, breaking the wires; or repeated bending in the sill harness transition area breaks the internal copper strands while leaving the insulation intact.
  • 4SRS ECU (airbag control module) internal fault: An internal ECU detection circuit fault causes a false open-circuit report. This condition usually triggers fault codes for multiple airbags simultaneously.
  • 5Clock spring or spiral cable-related fault: On some models, the knee airbag wiring harness passes under the steering wheel. An internal open circuit in the clock spring may affect circuit detection (verify the wiring harness routing for the specific model).
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the negative battery terminal, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment during repair.
  • 2
    Fault confirmation and freeze frame reading: Use a diagnostic tool such as VDS2000 or Launch PAD to read the complete fault codes and freeze frame data. Confirm whether the fault is current (Active) or historical (Historic). Record the vehicle status at the time of the fault.
  • 3
    Visual inspection: Remove the driver's side lower instrument panel trim and locate the left knee airbag assembly (inside the instrument panel below the steering column). Verify the yellow SRS connector is fully seated and the connector lock is engaged. Inspect the wiring harness for obvious damage, crushing, or signs of water ingress.
  • 4
    Circuit continuity check: Disconnect the airbag connector. Use a multimeter to measure the airbag-side igniter resistance (standard value: 2.0 ± 0.3 Ω). If the resistance is infinite, replace the airbag assembly. Measure harness-side continuity from the airbag ECU to the connector. Check for open circuits or shorts to ground.
  • 5
    Insulation and contact check: Inspect connector terminals for oxidation, backed-out pins, or deformation. Measure harness-to-ground insulation resistance (should be >1MΩ). Check the SRS ECU connector for looseness.
  • 6
    Component replacement: If testing confirms a faulty airbag assembly, replace it with an OEM left knee airbag (verify the part number by vehicle model; e.g., #... for the E2 model). Store the new airbag module flat and do not drop it. If the wiring harness is faulty, repair or replace the instrument panel wiring harness assembly.
  • 7
    System reset and verification: Reconnect all connectors and the battery. Use the diagnostic tool to clear the fault code and perform the 'SRS system self-check' (usually requires turning the ignition switch to the ON position and waiting for the system self-check to complete). Verify B17171B does not return and check that the instrument panel SRS warning light turns off after the self-check.
  • 8
    Functional test (optional): At an authorized service center, use the special tool to perform the 'SRS system simulation test' to verify the knee airbag circuit resistance value is within the normal range and ensure the system readiness status is Complete.
Real-World Cases
BYD DTC AI Analysis

New vehicle PDI found knee airbag not connected.

✓
A 2020 BYD E3 arrived at the dealer with the SRS warning light on steadily during PDI. Scanning retrieved DTCs B17171B (left knee airbag not connected) and B17181B (right knee airbag not connected). Inspection traced the fault to an assembly omission: the yellow SRS connectors for both knee airbags had not been plugged in when the instrument panel was installed on the production line. After reconnecting the connectors and confirming the locks were fully seated, the technician cleared the codes. The SRS system then passed self-test, and the fault was eliminated. This case suggests possible assembly issues on E2/E3 models from that production period.
BYD DTC AI Analysis

Corroded knee airbag wiring harness in flood-damaged vehicle

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After driving through floodwater in heavy rain, a 2019 Qin EV displayed an airbag warning light on the instrument panel. The scan tool retrieved current fault code B17171B. Removing and inspecting the driver-side knee airbag connector revealed obvious water staining and green copper corrosion inside the plug. Water level exceeded the floor while wading, allowing moisture to enter the SRS connector through poor harness sealing. Repairs: cleaned connector terminals with electronic cleaner, applied special conductive grease, replaced the waterproof seal, and waterproofed the harness. After repair, resistance returned to normal. Cleared the fault code, and it did not return.
BYD DTC AI Analysis

Loose connection in airbag circuit after accident repair

✓
A BYD E2 had a collision. During replacement of the front bumper and instrument panel, the repair technician removed the left knee airbag. After repairs, the technician did not clear the fault codes. Three days after delivery to the customer, the SRS warning light illuminated. Inspection found that although the knee airbag connector was plugged in, the locking tab had not fully engaged. Vehicle vibration caused an intermittent connection, triggering an intermittent B17171B fault. After reconnecting the connector and hearing a locking click, the technician used a diagnostic tool to perform 'Crash Data Clear' and 'SRS Configuration Write', permanently resolving the fault.
BYD DTC AI Analysis

Wiring harness wear caused an intermittent open circuit.

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An E3 with 80,000 km had an intermittent SRS warning light. The scan tool showed stored fault code B17171B. Inspection found the wiring harness under the dashboard chafing on the edge of the steering column mounting bracket. The damaged insulation caused the internal copper strands to partially fracture, opening the circuit at certain steering angles or when the body flexed. Repair: Spliced in a replacement wire (minimum 0.5mm², high-temperature grade), rerouted the harness to clear the interference point, wrapped the section with fleece tape and corrugated tubing, and repositioned the harness clips to provide enough slack.
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.