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 — Atto 3

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 Atto 3 indicates a high-severity short to ground in the front passenger right knee airbag squib circuit. This can stop the knee airbag deploying correctly and may put the SRS system into reduced protection mode. Common causes include damaged wiring 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 — Atto 3
  • 1Harness mechanical damage: Detached or improperly installed retaining clips cause the right knee airbag harness to rub against sharp metal edges when passing through the instrument panel frame or firewall. Prolonged friction damages the insulation, causing the copper core wire to contact the vehicle body ground directly.
  • 2Connector water ingress and corrosion: Water enters the right knee airbag connector (located low beneath the center console) during vehicle wading, A/C condensate leaks, or high-pressure washing, causing electrolytic corrosion between the terminals and creating a short circuit path.
  • 3Incorrect center console removal or installation: When repairing the air conditioning system or center control components, removing or installing the center console pinches the wiring harness between the dashboard and the body. Alternatively, an incompletely seated connector bends the terminals, causing them 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 dropping the 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 jolts and 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) and not a history fault. Check the right knee airbag circuit resistance in the data stream (should display <1Ω or short circuit).
  • 3
    Visual inspection: Remove the centre console right trim panel. Check the right knee airbag connector (usually a yellow plug) for a secure connection and verify the locking tab is fully seated. Inspect the wiring harness for obvious signs of pinching, abrasion, 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's resistance setting to directly measure an energized airbag). Normal resistance is 2.0±0.5Ω. If the reading is 0Ω or <1Ω, this indicates an internal short circuit in the airbag module.
  • 6
    Repair Procedure: If the wiring harness is damaged, repair the wire with solder and insulate it with double-layer heat-shrink tubing. Re-secure the harness to maintain a clearance of at least 20mm from metal components. If the connector has water ingress, clean it with electrical contact cleaner and dry it. Replace the connector if necessary. If the airbag module is faulty, replace the OEM knee airbag assembly.
  • 7
    System reset: Reconnect all connectors, install the centre console, 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 confirm B1722-00 does not reappear.
  • 8
    Function verification: Start the vehicle and confirm the airbag warning light turns off after the self-check (turning off after approximately 6 seconds is normal). Conduct a road test over rough roads. Observe whether the fault light illuminates again 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 Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.