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B1718-00

B1718-00 indicates a short to ground in the driver-side knee airbag ignition circuit — Qin Plus

Safety System

B1718-00 indicates a short to ground in the driver-side knee airbag ignition circuit.

In the BYD SRS (Supplemental Restraint System) architecture, this fault code indicates the airbag control module (ACM) detects the left knee airbag inflator circuit resistance is below the threshold (typically < 1.0Ω), identifying a short to ground.

This fault forces the entire airbag system into fail-safe mode and continuously illuminates the instrument cluster SRS warning lamp.

During a collision, the knee airbag may fail to deploy, and the fault may affect the deployment strategy for other front airbags.

This constitutes a hard fault.

Once confirmed, it remains active; cycling the ignition does not clear it.

The B1718-00 fault code on the Qin Plus indicates a high-severity short to ground in the driver-side knee airbag ignition circuit. The SRS warning light will stay on, and the knee airbag may not deploy correctly in a crash. Common causes include damaged wiring insulation or water ingress, corrosion, or bent pins at the knee airbag connector. 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 — Qin Plus
  • 1Knee airbag wiring harness wear or crushing damages the insulation layer, causing a short to ground against the metal body frame. This commonly occurs after vehicle wading or chassis modifications.
  • 2Water ingress, oxidation, or bent pins at the knee airbag connector (located under the driver-side dashboard, left of the steering column), causing a short circuit between the ignition circuit terminal and the ground terminal.
  • 3Internal igniter short circuit in the knee airbag module, typically due to continuity between the internal bridge wire and the housing, or a manufacturing batch defect.
  • 4SRS control module internal sampling circuit fault incorrectly identifying a normal low resistance as a short circuit, or internal power transistor breakdown.
  • 5Improper repair after a vehicle accident left the airbag wiring harness improperly secured, causing prolonged friction against the dashboard metal bracket and resulting in a short circuit.
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 capacitor. Wear an anti-static wrist strap to prevent accidental airbag deployment.
  • 2
    Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000/ED400) to read the fault code. Confirm B1718-00 is a current fault (Active). Record the resistance value in the freeze frame data (usually 0Ω or a very low value).
  • 3
    Visual inspection: Remove the driver-side lower dashboard trim panel. Check the left knee airbag connector (yellow waterproof plug) for looseness, water ingress, or corroded pins. Check the wiring harness for chafing where it passes through the dashboard frame.
  • 4
    Circuit measurement: Disconnect the auxiliary battery, wait, then disconnect the knee airbag connector. Use a multimeter to measure the resistance between the two airbag-side wires and body ground (should be > 1MΩ), and measure the resistance between the two wires (normal: 2.0-5.0Ω). If the wiring harness has continuity to ground, a short circuit exists.
  • 5
    Component isolation: If the wiring harness is normal, connect a dedicated airbag simulator (2.7Ω substitute resistor) in place of the knee airbag. Clear the DTC. If the fault disappears, replace the knee airbag assembly. If the fault persists, check the wiring harness continuity from the SRS ECU to the airbag.
  • 6
    Repair verification: After repairing the short circuit or replacing the faulty component, restore all connections and connect the battery. Use the diagnostic tool to clear the fault code and perform an SRS System Check. Confirm B1718-00 changes to a History fault and the SRS warning lamp turns off. Finally, perform a road test to verify the repair.
  • 7
    System calibration: On some models, use the diagnostic tool to perform 'Configuration and Calibration' → 'SRS Configuration'. Write the correct airbag configuration code to ensure the system recognizes the knee airbag has returned to normal.
Real-World Cases
BYD DTC AI Analysis

Qin EV450 knee airbag short circuit repair after water ingress

✓
A 2018 BYD Qin EV450 presented with the SRS warning light staying on after heavy rain and wading through floodwater. Retrieved DTC B1718-00 (left knee airbag short to ground). Found severe water ingress in the driver-side carpet. The knee airbag connector (located under the steering column) contained water, and its pins had oxidised and blackened. Removed the connector and cleaned it with anhydrous ethanol. After blow-drying, measured the harness resistance to ground; it returned to normal (infinite). Replaced the connector with a new waterproof one and applied conductive grease. Cleared the DTC and the SRS system returned to normal. Recommend checking the vehicle floor seals to prevent future water ingress.
BYD DTC AI Analysis

Qin 80: Aftermarket steering wheel installation damaged wiring harness

✓
A 2017 Qin 80 developed fault code B1718-00 one week after the owner fitted a racing steering wheel. Diagnosis revealed that during instrument panel removal for the modification, the edge of the instrument panel metal bracket cut through the insulation of the knee airbag wiring harness. This allowed copper strands to directly contact the vehicle frame, creating a short to ground. Wrapped the damaged section with insulation tape, rerouted the harness through dedicated corrugated tubing, and secured it to the wiring harness bracket to avoid contact with sharp edges. Cleared the fault codes and performed repeated bump tests; the fault did not return. Reminder: professionals must carry out any modifications involving the SRS system.
BYD DTC AI Analysis

Replaced Qin 100 knee airbag assembly due to internal short circuit

✓
A 2017 Qin 100 with no accident or flood history had an intermittent SRS warning light. The scan tool showed B1718-00 appearing intermittently. We measured the knee airbag harness resistance to ground and found it normal, but shaking the airbag unit caused the resistance to jump to 0Ω. We removed the left knee airbag (located behind the storage compartment under the dashboard), substituted a dedicated simulator, and the fault disappeared. This confirmed an intermittent short in the airbag's internal igniter. We replaced the left knee airbag module with a new unit (part number: EG-5823010), performed system configuration writing, and resolved the fault. The old part was returned to the manufacturer, whose analysis found a defect in the internal bridge wire insulation.
BYD DTC AI Analysis

Qin EV300 SRS ECU False Positive Fault Troubleshooting

✓
A 2017 Qin EV300 stored DTC B1718-00 following collision repairs. Replaced the knee airbag, but the fault persisted. Measured the airbag circuit resistance at 2.3 Ω (normal), yet the scan tool still indicated a short to ground. Suspected internal sampling circuit damage in the SRS ECU (located beneath the center console). Inspected the ECU connector and found no faults; measured continuity between the ECU and airbag wiring and found it normal. Tried replacing the SRS ECU with an identical unit (requires online immobilizer and VIN matching). After replacement, the fault cleared, confirming an internal control module failure. Note: Replacing the SRS ECU requires online programming and safety configuration writing using the BYD dedicated diagnostic tool.
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC 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.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 Qin Plus →Qin Plus 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.