AU
B1723-00

B1723-00 indicates the Supplemental Restraint System (SRS) detected a short to vehicle power (B+, 12V) in the ignition circuit (squib circuit) of the right knee airbag (passenger-side knee airbag, typically located below the right side of the dashboard) — Seal U

Safety System

B1723-00 indicates the Supplemental Restraint System (SRS) detected a short to vehicle power (B+, 12V) in the ignition circuit (squib circuit) of the right knee airbag (passenger-side knee airbag, typically located below the right side of the dashboard).

Under normal conditions, the SRS control unit (ACU) maintains a specific voltage across the airbag inflator terminals (typically a 5V or 12V pulse diagnostic voltage), and circuit resistance measures between 2.0 and 3.0 Ω.

When the ACU detects the circuit voltage remains at or near battery voltage (>10V), it identifies a short to power.

This fault can cause: 1) the right knee airbag to fail to deploy properly during a collision; 2) the SRS to enter fail-safe mode, disabling all airbag functions; 3) a potential risk of unintended airbag deployment.

This severe-level fault requires immediate repair.

The B1723-00 fault code on the Seal U indicates a high-severity short to 12V power in the passenger-side right knee airbag ignition circuit. This can stop the airbag deploying correctly, disable SRS functions, or risk unintended deployment. Common causes include damaged under-dash wiring, aged insulation, water ingress, corrosion, or a deformed yellow airbag connector. Have the vehicle inspected and repaired by an authorised dealer immediately. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged right knee airbag wiring harness or aged insulation contacts vehicle power wiring (such as a constant 12V circuit), causing a short circuit. This commonly occurs at the wiring harness pass-through hole under the dashboard or near the steering column.
  • 2Water ingress, corrosion, or terminal deformation at the airbag connector (usually a yellow plug) causing a short circuit between terminals, especially after vehicle wading or an air conditioning condensate leak.
  • 3During instrument panel (IP) removal and repair, a pinched wiring harness, damaged retaining clips, or worn harness protective sleeve exposes copper wire, causing contact with the metal frame or power wire.
  • 4Knee airbag module internal igniter short circuit (very rare; typically results from internal manufacturing defects or previous severe vibration).
  • 5SRS control unit (ACU) internal driver circuit fault, false detection, or actual internal short circuit (rule out wiring harness issues before confirming).
What To Do
  • 1
    Safety preparation: Power down the vehicle, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS backup capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use a BYD dedicated diagnostic tool (VDS or ED400) to read fault codes. Confirm B1723-00 is a current fault (Active) and check for accompanying fault codes (e.g., B1722, B1724).
  • 3
    Visual inspection: Remove the right knee trim panel (below the glove box or lower right trim panel) and check the right knee airbag yellow connector for looseness, water ingress, corrosion, or obvious burn marks.
  • 4
    Circuit measurement: Disconnect the airbag connector. Use a multimeter to measure voltage to ground on the wiring harness side (not the airbag side). A 12V reading confirms a short to power. Measure resistance to ground; if the reading is 0 Ω, locate the short.
  • 5
    Harness inspection: Trace the instrument panel harness (IP Harness) toward the SRS control unit. Closely inspect interference points between the harness and the instrument panel metal bracket, steering column, and air conditioning duct. Look for damage or crush marks.
  • 6
    Section isolation: If necessary, disconnect the intermediate connector (e.g., instrument panel wiring harness to body wiring harness connector). Measure in sections to narrow down the fault location and determine whether the short circuit is on the airbag module side or the wiring harness side.
  • 7
    Fault repair: Repair the damaged wiring harness (protect with waterproof tape and corrugated conduit) or replace the damaged connector. If the airbag module has an internal short circuit, replace the right knee airbag assembly.
  • 8
    System verification: Restore all connections, reconnect the battery, and clear fault codes. Perform the SRS system self-test (Key Cycle 3 times). Verify the fault code does not return and the instrument panel airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Knee airbag connector water ingress short circuit in water-wading vehicle

✓
A 2017 Qin EV300. The owner reported the airbag warning light stayed on constantly. Diagnostic scanning retrieved fault code B1723-00 (right knee airbag short to power). The vehicle had previous water ingress. The right knee airbag connector (beneath the center console) showed visible water stains and green corrosion inside — electrolytic corrosion caused a micro-short between the terminals. After cleaning and blow-drying the connector, the wiring harness measured normal. Replacing the airbag wiring harness connector with a new part resolved the fault. Recommend checking the A/C drain tube for blockages that could cause water leaks.
BYD DTC AI Analysis

Dashboard wiring harness crushed and shorted after accident repair

✓
A 2018 Qin EV450 logged DTC B1723-00 after front collision repairs. Inspection found that during the accident repair involving dashboard removal and reinstallation, the right knee airbag harness was not routed to specification. The instrument panel metal bracket pinched the harness, damaging its insulation and causing internal wires to contact the bracket (ground) and nearby power lines, creating a short circuit. The technician rerouted the harness, repaired the damaged wires (adding insulation sleeving), and installed a protective rubber sleeve between the harness and bracket, clearing the fault.
BYD DTC AI Analysis

Aftermarket dash cam installation caused wiring interference

✓
A 2017 Qin 100 came in with the airbag light on after an aftermarket dashcam was installed and its power tapped. Stored fault codes: B1723-00 and B1722-00 (left knee airbag). Inspection found the installer had bundled the dashcam constant 12V power wire with the knee airbag harness under the centre console, and the cable tie securing the bundle pierced the airbag wire insulation, causing a short to power. The technician separated the harnesses, re-insulated the damaged section, and relocated the power feed to the standard fuse box tap point, which resolved the fault.
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.