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 8

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 8 indicates a short to ground in the right knee airbag squib circuit, causing the SRS warning lamp to turn on. This is a high-severity fault because the knee airbag may not deploy in a crash. Common causes include damaged wiring insulation 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 8
  • 1Wiring harness mechanical damage: Detached or improperly installed retaining clips allow 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 directly contact the vehicle body ground.
  • 2Connector water ingress and corrosion: Water entering the right knee airbag connector (located low under the center console) during vehicle wading, A/C condensate leakage, or high-pressure washing causes electrolytic corrosion between the terminals, creating a short-circuit path.
  • 3Improper removal and installation of the center console: Pinching the wiring harness between the dashboard and the body when removing or installing the center console to repair the air conditioning system or central control components. Failing to fully seat the connector bends the terminals, causing them to contact the metal frame.
  • 4Airbag module internal fault: Inflator internal igniter short circuits due to quality issues or prolonged exposure to high-temperature and high-humidity environments, causing resistance to drop abnormally to nearly 0 Ω.
  • 5Wiring aging and damage: After extended vehicle use (typically over 5 years), wiring harness insulation naturally ages and cracks, making intermittent contact with metal body components during vehicle bumps and vibration.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds for the SRS system energy storage capacitor to discharge completely. 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. 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. Check the right knee airbag connector (usually a yellow plug) for a secure connection and a fully seated locking tab. Inspect the wiring harness for obvious signs of crushing, 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 infinite (OL). If continuity exists, trace the wiring 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 in resistance mode to directly measure an energized airbag). Normal resistance is 2.0±0.5Ω. If the reading is 0Ω or <1Ω, the airbag module has an internal short circuit.
  • 6
    Repair procedure: If the wiring harness is damaged, solder the wire, insulate with double-layer heat-shrink tubing, and re-secure the harness maintaining at least a 20mm clearance from metal components. If the connector has water ingress, clean with electrical contact cleaner and dry thoroughly; replace the connector if necessary. If the airbag module is faulty, replace with an OEM knee airbag assembly.
  • 7
    System reset: Reconnect all connectors, install the center 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 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 and observe if the fault light illuminates again when driving over bumpy roads to 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 Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.