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 — Seal U

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 Seal U indicates a high-severity short to ground in the front passenger right knee airbag squib circuit. This can stop the knee airbag from deploying in a crash and may put the SRS system into reduced protection mode. Common causes include damaged wiring insulation rubbing on metal parts or water/corrosion in the airbag connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Wiring harness mechanical damage: Detached or improperly installed retaining clips cause the right knee airbag wiring harness to rub against sharp metal edges where it passes through the instrument panel frame or firewall. Prolonged friction damages the insulation, causing the copper core to directly contact the vehicle body ground.
  • 2Connector water ingress and corrosion: During vehicle wading, A/C condensate leakage, or high-pressure car washing, water enters the right knee airbag connector (located low under the center console), causing electrolytic corrosion between the terminals and creating a short-circuit path.
  • 3Improper center console removal and installation: When repairing the air conditioning system or center control components, the removal and installation process pinches the wiring harness between the instrument panel and the body, or incomplete connector insertion bends the terminal, causing it to contact the metal frame.
  • 4Airbag module internal fault: The inflator igniter develops an internal short circuit due to a quality issue or prolonged exposure to high temperatures and humidity, causing resistance to drop abnormally to near 0 Ω.
  • 5Wiring aging and damage: After extended vehicle service (typically over 5 years), wiring harness insulation naturally ages and cracks, causing intermittent contact with metal body components during vehicle vibration or bumps.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system energy storage capacitor. Place an 'Airbag Under Repair' warning sign 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) connects securely and the locking tab seats fully. Inspect the wiring harness for obvious pinching, wear, signs of 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-side) connector. Normal reading is infinity (OL). If continuity exists, inspect the wiring harness up to the SRS control unit, focusing on the firewall wiring grommet and 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 an energized airbag). The normal resistance is 2.0 ± 0.5 Ω. If the reading is 0 Ω or <1 Ω, the airbag module has an internal short circuit.
  • 6
    Repair procedure: If the wiring harness is damaged, solder the wire, insulate it with double-layer heat-shrink tubing, and re-secure the harness, maintaining at least a 20mm clearance from metal parts; if water enters the connector, clean it with electrical contact cleaner, dry it thoroughly, and replace the connector if necessary; if the airbag module is faulty, replace it with a genuine knee airbag assembly.
  • 7
    System reset: Reconnect all connectors, install the center console, connect the battery negative terminal, clear the fault code using the diagnostic tool, perform the 'SRS System Self-Test' or 'Crash Sensor Calibration' procedure, and confirm B1722-00 does not return.
  • 8
    Function verification: Start the vehicle and confirm the airbag warning lamp turns off after the self-check (turning off after about 6 seconds is normal). Perform a road test and observe whether the fault lamp illuminates again when driving over bumpy roads to confirm the fault is completely resolved.
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 Seal U Fault Codes
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.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.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.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.