AU
B1680

This DTC indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal signal from the passenger airbag cutoff switch (PAD switch) — Qin Plus

Safety System

This DTC indicates the airbag control unit (SRS ECU) detects a communication loss or abnormal signal from the passenger airbag cutoff switch (PAD switch).

Typically located on the right side of the center console or inside the glovebox, this switch manually controls the front passenger airbag activation/deactivation status (e.g., when installing a child safety seat).

The ECU triggers DTC B1680 if it fails to detect a valid resistance signal within a set cycle (normal operation uses different resistance values to distinguish ON/OFF positions, such as 2.2kΩ/4.7kΩ) or detects an open circuit (infinite resistance).

This fault causes: 1) the front passenger airbag status to enter an unknown mode, where the system may default to disabling the airbag to prevent unintended deployment, reducing crash protection; 2) the instrument panel airbag warning light to illuminate continuously; 3) some models to record abnormal crash event readiness data, affecting accident liability determination.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Switch connector loose or disconnected: Commonly occurs after removing or installing the dashboard, replacing the A/C filter, repairing the center console, or retrofitting a large display, when technicians fail to securely reconnect the PAD switch plug, or a broken locking clip causes a poor connection.
  • 2PAD switch assembly internal fault: Internal carbon film resistor wear, contact oxidation or sulfidation, or leaf spring fatigue causes the output resistance to exceed the ECU recognition range (typically ±5% tolerance), especially on vehicles operated in high-humidity areas.
  • 3Wiring harness open or short circuit: Sharp frame edges wear through the internal dashboard wiring harness, rodents chew the wires, or accident repairs crush the harness, causing the signal wire (usually the yellow wire) to open or short to ground.
  • 4Mechanical binding at the switch mounting position: The switch fails to fully snap into the mounting base, preventing the internal sliding contact from reaching its position, or a deformed mounting base tilts the switch, causing poor connector contact.
  • 5SRS ECU sampling circuit fault: Damaged internal ECU pull-up resistor or A/D converter causing the ECU to falsely detect a switch open-circuit status, or lost software calibration data (rare, usually accompanied by other SRS fault codes).
What To Do
  • 1
    Diagnostic tool deep scan: Use the VDS2000 or a dedicated BYD diagnostic tool to read the B1680 freeze frame data. Confirm the fault frequency (intermittent/continuous), ambient temperature, and voltage at the time of occurrence. Check for accompanying SRS communication fault codes.
  • 2
    Physical connection check: Locate the PAD switch (usually on the right side of the glove box for Song MAX/Yuan EV; on the right side of the center console for Tang/Qin). Visually verify the connector is fully seated, confirm the locking mechanism (CPA lock) is intact, and gently pull the wiring harness to confirm it is secure.
  • 3
    Wiring harness and terminal inspection: Disconnect the negative battery terminal and wait at least 90 seconds to discharge system capacitors (to prevent accidental airbag deployment). Unplug the switch connector and inspect terminals for oxidation, backing out, or enlarged sockets. Clean with electrical contact cleaner and inspect the wiring harness sheath for abrasion.
  • 4
    Switch function test: Remove the switch and use a multimeter to measure the resistance in the ON and OFF positions. Compare the readings against the repair manual specifications (typically 2.0-2.5kΩ for ON, 4.5-5.0kΩ for OFF, ±5% tolerance). Check the switch operating torque and inspect for binding.
  • 5
    Circuit continuity and insulation test: Use a multimeter to measure signal wire continuity (resistance <1Ω) and insulation to ground and power (>10MΩ) between the switch connector and the SRS ECU connector (usually located under the center console or floor center). Closely inspect the instrument panel frame for interference points.
  • 6
    ECU and calibration verification: If wiring and switch are normal, check the SRS ECU software version (some pre-2020 models require an upgrade). Verify the correct front passenger airbag status in the vehicle configuration code (VIN configuration). Replace the ECU and perform online programming if necessary.
  • 7
    System verification and testing: After restoring connections, turn the ignition switch to the ON position. Confirm the instrument cluster airbag warning light turns off after the self-check (approximately 6 seconds). Use the diagnostic tool to read the data stream. Operate the switch and verify the 'Passenger Airbag Cutoff Switch' status switches between 'Enabled' and 'Disabled'. Finally, execute the SRS system cycle test.
Real-World Cases
BYD DTC AI Analysis

Forgot to reconnect PAD switch connector after dashboard removal and refitting on Song MAX.

✓
A 2019 Song MAX with 32,000 km. The customer reported the airbag warning light staying on constantly. Service history showed a non-authorised workshop had replaced the AC evaporator core one week earlier. The diagnostic tool retrieved current DTC B1680 with no other accompanying faults. Removing the glovebox revealed the PAD switch connector completely detached — the technician had missed this connection during instrument panel reassembly. Reconnected the plug and confirmed the CPA lock was engaged. Cleared the fault codes, and the airbag light went out. The data stream showed the switch status changing normally when operated.
BYD DTC AI Analysis

Internal oxidation of the switch caused intermittent fault on Yuan EV

✓
2020 Yuan EV535 with 50,000 km. Intermittent airbag warning light; DTC B1680 alternated between history and current codes. Inspected the switch connector—found it secure—but the switch resistance drifted (standard ON resistance should be 2.4 kΩ, but it fluctuated between 1.2–3.8 kΩ and was unstable). Disassembled the switch and found the internal carbon film contacts oxidised due to humidity. Replaced the passenger airbag switch (part number: KZ-5820100) and monitored continuously for a week. The fault did not recur, and the resistance remained stable within the standard range.
BYD DTC AI Analysis

Hidden open circuit in Tang DM wiring harness after accident repair

✓
2021 Tang DM. After right-front collision repairs, the instrument cluster displayed an airbag fault. Read DTCs B1680 and B167E (right rear side impact sensor communication error). Inspection found the passenger-side A-pillar harness crushed in the accident. The PAD switch signal wire (yellow, Pin 2) had a 'hidden break' — internal copper strand fracture with intact insulation — causing an intermittent connection. Stripped and re-soldered the broken wire, reinforced the insulation with heat-shrink tubing, and rerouted the harness away from the body frame. This resolved the fault, and both DTCs disappeared.
BYD DTC AI Analysis

Switch not fully seated on Qin Pro petrol variant, causing poor contact.

✓
2020 Qin Pro. Customer bought a large-screen nav unit online, removed and refitted the centre console themselves, after which the instrument cluster showed an airbag fault. Scanned and found DTC B1680. On inspection, the PAD switch had been fitted backwards and not fully pushed into its mounting hole, preventing the connector from fully mating — only one side of the pins was making contact. Reoriented the switch correctly, clicked the retaining clip fully home (audible click), and pushed the connector in to full insertion depth (secondary locking click heard). Cleared the DTC; it did not return. Advised the customer to leave all airbag system work to a qualified professional.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.