UAE
AU
B1718-00

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

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.

4
Cases Logged
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 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.