AU
B1718-00

B1718-00 indicates a short to ground in the driver-side knee airbag ignition circuit — Atto 8

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 Atto 8 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 and bent/oxidised connector pins. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1A worn or crushed knee airbag wiring harness damages the insulation layer, causing contact with the metal body frame and creating a short to ground. This commonly occurs after driving through water or modifying the chassis.
  • 2Oxidation due to water ingress or bent pins in the knee airbag connector (located under the driver-side instrument panel, left of the steering column) cause a short circuit between the ignition circuit terminal and the ground terminal.
  • 3Internal short circuit in the knee airbag module igniter, usually due to the internal bridgewire shorting to the housing or a manufacturing batch defect.
  • 4Internal fault in the SRS control module sampling circuit misinterpreting normal low resistance as a short circuit, or internal power transistor breakdown.
  • 5Improper post-accident repair left the airbag wiring harness incorrectly secured, leading to prolonged rubbing against the dashboard metal bracket and causing 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 for the SRS capacitor to fully discharge. 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 (typically 0Ω or extremely low).
  • 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 pin corrosion. Check the wiring harness for chafing where it passes through the dashboard frame.
  • 4
    Circuit measurement: Disconnect the backup 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 > 1 MΩ). Measure the resistance between the two wires (normal: 2.0-5.0 Ω). Continuity to ground indicates a short circuit.
  • 5
    Component isolation: If the wiring harness is normal, use a dedicated airbag simulator (substitute resistor 2.7Ω) in place of the knee airbag. Clear the fault code. 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. Verify DTC B1718-00 changes to History and the SRS warning light 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 Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.