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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.

5
Cases Logged
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.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.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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.