AU
B1719

DTC B1719 indicates a short to B+ in the Driver Side Knee Airbag squib circuit — Qin Plus

Safety System

DTC B1719 indicates a short to B+ in the Driver Side Knee Airbag squib circuit.

In the SRS (Supplemental Restraint System) architecture, the knee airbag squib is a low-value resistor (standard value 2.0 ± 0.3 Ω).

Under normal conditions, the airbag ECU triggers the squib by controlling the ground circuit.

When the diagnostic system detects the circuit voltage continuously exceeding the threshold (typically above 4.5V, approaching the 12V battery voltage), it identifies a short to power.

This fault results in the following: 1) The ECU actively disables the airbag circuit, preventing deployment during a collision and resulting in a loss of driver leg protection. 2) A potential safety risk exists; in extreme cases, circuit abnormalities may cause unintended airbag deployment. 3) The SRS enters fail-safe mode and continuously illuminates the instrument cluster airbag warning light.

Inspect for damaged wiring harness insulation, misaligned connector terminals, electrolytic short circuits caused by fluid ingress, and internal short circuits within the airbag module squib.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Long-term friction between the knee airbag wiring harness and the instrument panel metal frame or steering column edge damages the insulation, causing a short circuit to the constant power supply wire.
  • 2Internal short circuit in the knee airbag assembly igniter (squib) due to manufacturing defects, moisture ingress, or aging, resulting in abnormally low resistance.
  • 3Terminals in the yellow SRS dedicated connector under the driver's dashboard are bent, backed out, or improperly seated, contacting an adjacent power pin (such as constant 12V).
  • 4Vehicle wading, deep interior cleaning, or A/C condensate leaks cause liquid to enter the connector, resulting in an electrolytic short circuit between terminals.
  • 5An improperly secured wiring harness after accident repairs or modifications allows the steering column universal joint, pedal mechanism, or seat rail to pinch the harness, damaging the insulation and causing a short circuit.
What To Do
  • 1
    Safe power-off: Turn off the ignition switch, disconnect the negative battery cable, and wait at least 3 minutes to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the driver's side lower dashboard trim panel (knee bolster). Inspect the yellow 2-pin knee airbag connector and wiring harness for damage, burn marks, water ingress, or modification crimp marks.
  • 3
    Resistance measurement: Disconnect the airbag connector. Use a digital multimeter to measure the resistance between the two terminals of the knee airbag igniter. The standard value is 2.0±0.3 Ω. If the resistance is below 1.0 Ω or 0, this indicates an internal airbag short circuit. Replace the assembly.
  • 4
    Voltage check: Reconnect the battery (do not connect the airbag connector). Back-probe the harness-side connector terminal to measure the voltage. The normal reading should be close to 0V (ECU internal pull-down resistor). A 12V battery voltage reading confirms a short to power.
  • 5
    Harness continuity check: Disconnect the airbag ECU connector. Test the wiring harness between the knee airbag connector and the ECU for a short circuit to the power supply line (constant B+). Focus the inspection on the dashboard wiring harness tie points and pass-through holes.
  • 6
    Insulation repair: If the wiring harness is damaged, wrap it with double-layer heat-shrink tubing. Reroute the harness to avoid moving parts (such as the steering column, accelerator pedal, and seat rails).
  • 7
    Component replacement: If testing confirms an internal short circuit in the airbag, replace the driver's knee airbag assembly (Note: Do not measure resistance on the new part before installation to prevent static current from causing accidental deployment).
  • 8
    System reset: After installation, reconnect the battery. Use VDS or a dedicated diagnostic tool to clear the fault code. Perform the SRS system self-check (approximately 3-5 ignition cycles). Verify B1719 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Modified seat rails crushed the knee airbag wiring harness on a Song Pro, causing a short circuit

✓
The SRS warning light stayed on. VDS read DTC B1719 (left knee airbag short to power). The owner told us they had recently retrofitted electric seats. We removed the lower dash panel and found the seat rail mounting bolt had punctured the knee airbag wiring harness, damaging the insulation and shorting it to constant power. We measured 12V at the knee airbag connector to ground, with only 0.5 Ω resistance. We repaired the damaged harness using double-layer heat shrink tubing, rerouted the wiring clear of the seat track travel path, replaced the damaged yellow SRS connector, and cleared the fault codes. After clearing the codes, the system passed self-diagnosis. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Water ingress during interior cleaning caused knee airbag connector oxidation and short circuit on Qin Plus DM-i

✓
After starting the vehicle, the dashboard displayed 'Check SRS System' and the airbag warning light came on. The scan tool read DTC B1719. The owner said they had done a deep interior cleaning the previous day, and a large amount of liquid flowed into the driver-side floor. Removed the knee airbag connector located under the instrument panel to the left of the steering column. Pins showed severe oxidation and green copper corrosion. Measured the resistance between the signal wire and power pin and found it abnormal. Repair: Cleaned the connector terminals thoroughly with electronic cleaner, applied conductive grease to prevent corrosion, replaced the waterproof connector retaining clip to ensure a proper seal, reconnected the connector, cleared the fault code, and the system returned to normal.
Original source ↗
BYD DTC AI Analysis

Tang DM: knee airbag harness root fatigue fracture, intermittent short to power

✓
The SRS light illuminated intermittently on rough roads but stayed off on smooth ones. The diagnostic tool displayed intermittent DTC B1719. A static measurement showed the knee airbag resistance was normal (2.1 Ω), but shaking the wiring harness below the dashboard caused the resistance to jump to infinity, and a 12V reading occasionally appeared. Disassembly revealed that the knee airbag harness had broken internal copper wires at the point where they exit the dashboard frame due to long-term vibration. The broken ends occasionally contacted adjacent power wires during vibration. Solution: Replaced the knee airbag wiring harness assembly (including the connector), re-secured the harness with enough slack to stay clear of the steering column travel range, and road tested 50 km with no fault recurrence.
Original source ↗
BYD DTC AI Analysis

Yuan Pro: After accident repair, knee airbag connector locking tab broken, poor contact

✓
Vehicle repaired after front collision (dashboard replaced). Post-repair, airbag warning light stayed on, storing DTC B1719. Inspected the newly replaced knee airbag and SRS ECU. Found the knee airbag connector appeared plugged in, but its internal locking tab had broken in the accident, causing the terminal to back out and contact the adjacent constant-power pin, creating a short circuit. Also found poor ground at the SRS ECU earth point due to residual paint. Repair: Sanded the ECU earth point to achieve ground resistance below 1 Ω. Replaced the knee airbag connector (repair kit). Re-performed SRS configuration write and 'collision output clear' procedures. Fault fully resolved.
Original source ↗
BYD DTC AI Analysis

Han EV knee airbag internal igniter short circuit caused abnormal resistance.

✓
The vehicle had no collision history, but the SRS light came on suddenly with DTC B1719. After disconnecting the knee airbag connector, we checked the harness side: no short to power (0V). The airbag assembly side (igniter) resistance measured 0.6 Ω, well below the standard 2.0 Ω, indicating an internal short in the knee airbag igniter. Further inspection found a tiny crack in the airbag housing sealant, likely allowing moisture to cause the short. We replaced the driver's side knee airbag assembly (confirmed the part number matched the vehicle configuration), then used VDS for ECU coding and matching, cleared the fault codes, and ran the system self-test. The airbag light went out.
Original source ↗
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.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.