AU
B1722-00

DTC B1722-00 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance connection to body ground (short to ground) in the right knee airbag (front passenger side knee airbag) squib circuit — Qin Plus

Safety System

DTC B1722-00 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance connection to body ground (short to ground) in the right knee airbag (front passenger side knee airbag) squib circuit.

The knee airbag contains a gas generator electrothermal igniter (typical resistance 2 ± 0.5 Ω).

The SRS module determines circuit integrity by monitoring circuit current and resistance.

If damaged wiring harness insulation contacts vehicle body metal, water enters the connector causing a short between terminals, or the internal airbag module igniter shorts, circuit resistance drops to nearly 0 Ω.

The control unit immediately cuts power to the circuit and illuminates the airbag fault warning lamp to prevent unintended airbag deployment or insufficient ignition energy.

In this condition, the right knee airbag fails to deploy during a collision, and the entire SRS system may enter a degraded protection mode.

The B1722-00 fault code on the Qin Plus indicates a high-severity short to ground in the front passenger right knee airbag squib circuit. This can stop the knee airbag from deploying and may put the SRS system into reduced protection mode. Common causes include damaged wiring insulation rubbing on metal or water/corrosion in the airbag connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Wiring harness mechanical damage: Detached retaining clips or improper installation allow the right knee airbag wiring harness to chafe against sharp metal edges when passing through the instrument panel frame or firewall. Prolonged friction damages the insulation, causing the copper core wire to directly contact the vehicle body ground.
  • 2Connector water ingress and corrosion: Water enters the right knee airbag connector (located low under the center console) during vehicle wading, A/C condensate leakage, or high-pressure car washing, causing electrolytic corrosion between terminals and creating a short circuit path.
  • 3Improper center console removal and installation: Removing or installing the center console during air conditioning system or center control component repairs pinches the wiring harness between the dashboard and the body. Alternatively, incomplete connector insertion bends the terminal, causing it to contact the metal frame.
  • 4Airbag module internal fault: Inflator internal igniter quality issues or prolonged exposure to high-temperature and high-humidity environments cause an internal short circuit, abnormally reducing resistance to near 0 Ω.
  • 5Wiring aging and damage: After extended vehicle use (typically over 5 years), the wiring harness insulation naturally ages and cracks, causing intermittent contact with metal body components during vehicle bumps or vibrations.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor. Place 'Airbag Under Repair' warning signs on the steering wheel and instrument panel.
  • 2
    Fault confirmation: Connect the BYD VDS or Launch X-431 diagnostic tool. Enter the SRS system to read fault codes and confirm B1722-00 is a current fault (Active), not a history fault. Check the right knee airbag circuit resistance value in the data stream (should display <1Ω or short circuit).
  • 3
    Visual inspection: Remove the center console right trim panel. Verify the right knee airbag connector (usually a yellow plug) is securely connected and the locking tab is in place. Inspect the wiring harness for obvious signs of crushing, wear, water ingress, or green copper corrosion.
  • 4
    Circuit isolation test: Disconnect the right knee airbag connector. Use a multimeter to measure resistance to ground at the harness-side (vehicle body side) connector. Normal resistance is infinity (OL). If continuity exists, inspect the wiring to the SRS control unit, focusing on the firewall wiring grommet and the instrument panel mounting bracket.
  • 5
    Component test: Carefully measure the resistance between the two pins of the airbag module-side connector (never use a multimeter resistance setting to directly measure a live airbag). The normal resistance is 2.0±0.5Ω. A reading of 0Ω or <1Ω indicates an internal short circuit in the airbag module.
  • 6
    Repair procedure: If the wiring harness is damaged, solder the wire, insulate with double-layer heat-shrink tubing, and re-secure the harness to maintain at least a 20mm clearance from metal components. If water enters the connector, clean with electronic contact cleaner and dry, replacing the connector if necessary. If the airbag module fails, replace with an OEM knee airbag assembly.
  • 7
    System reset: Reconnect all connectors, install the center console, and connect the negative battery terminal. Use the diagnostic tool to clear the fault code. Perform the 'SRS system self-check' or 'crash sensor calibration' procedure, and verify B1722-00 does not return.
  • 8
    Function check: Start the vehicle and confirm the airbag warning light turns off after the self-check (turning off after about 6 seconds is normal). Perform a road test. Observe if the fault light illuminates again when driving over bumpy roads, and confirm the fault is completely eliminated.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro EV - Centre console wiring harness chafed and shorted

✓
Symptoms: Instrument panel airbag warning light constantly illuminated. Scan tool retrieved code B1722-00. Vehicle recently had the center console removed and refitted. Diagnosis: Inspected the right knee airbag wiring harness and found the insulation chafed at the instrument panel frame mounting bracket. The bare copper wire was directly contacting the metal bracket, causing a short to ground. Measured resistance near 0Ω. Resolution: Repaired the damaged wiring with heat shrink tubing. Rerouted the harness and added securing clips. Cleared the fault code and the system returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Song PLUS DM-i - Water ingress into connector causing corrosion and short circuit

✓
After washing the car, the airbag warning light suddenly came on. Scanning showed historical fault codes B1722-00 and B1721-00. Inspecting the right knee airbag connector revealed water stains and green copper corrosion inside. Pressure washer spray directed under the centre console caused water ingress; the moisture created a low-resistance path between the pins and ground. Replaced the right knee airbag harness connector, cleaned the airbag module pins, and added extra waterproofing to the connector. Fault resolved.
BYD DTC AI Analysis

BYD Han EV – Intermittent short circuit on rough roads

✓
Symptom: Airbag warning light illuminated intermittently while driving; DTC B1722-00 logged as intermittent fault. Diagnosis: Performed wiggle test - fault code reappeared when moving the wiring harness below the dashboard. Disassembly revealed the firewall harness retaining clip had come loose. The harness was rubbing against the body frame, wearing through the insulation and creating an intermittent short to earth. Resolution: Cut out the damaged section, re-soldered and re-insulated the wiring. Rerouted and secured the harness correctly, fitted protective sleeving, and road tested - all normal.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM - Improperly reinstalled centre console

✓
Symptoms: After the dealership serviced the air conditioning system (removing the centre console) and handed over the vehicle, the airbag warning light came on. DTC B1722-00 was stored. Diagnosis: Inspection found the right knee airbag connector not fully seated (no lock click) and the wiring harness pinched between the dashboard frame and plastic trim, causing damage. Fix: Replaced the damaged wiring harness section. Reinstalled the centre console properly to prevent harness pinching, tightened fasteners to standard torque, and cleared the fault.
BYD DTC AI Analysis

BYD Yuan EV – Airbag module internal igniter short circuit

✓
Symptoms: No prior repair history. Airbag warning light suddenly illuminated and remained on. DTC B1722-00 could not be cleared. Diagnosis: Disconnected the airbag connector and measured harness-side to ground resistance — open circuit (normal). Measured airbag module resistance — near 0 Ω (normal: 2–3 Ω). Installed the faulty module in a known-good vehicle and reproduced the fault, confirming an internal short in the airbag module. Resolution: Replaced the right knee airbag module. After clearing the fault codes, performed an SRS system simulation test. Confirmed normal communication and delivered the vehicle.
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.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.