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) — Atto 8

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.

The B1680 fault code on the Atto 8 indicates a communication loss with the passenger airbag cutoff switch. This medium severity issue typically stems from a loose connector or internal switch failure, causing the airbag warning light to stay on and potentially disabling the passenger airbag. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available based on recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Loose or disconnected switch connector: Commonly occurs after removing or installing the dashboard, replacing the cabin air filter, repairing the center console, or retrofitting a large display. This results from failing to fully seat the PAD switch connector or from a broken locking clip causing a poor connection.
  • 2PAD switch assembly internal fault: Internal carbon film resistor wear, contact oxidation or sulfidation, or spring plate fatigue causes the output resistance value to fall outside the ECU recognition range (typically ±5% tolerance), especially on vehicles operated in high-humidity areas.
  • 3Wiring harness open or short circuit: Sharp frame edges, rodents, or crushing during accident repairs damage the internal dashboard wiring harness, causing the signal wire (usually the yellow wire) to open or short to ground.
  • 4Mechanical binding at the switch installation position: The switch fails to fully snap into the mounting base, preventing the internal sliding contact from seating properly, 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 incorrectly detect a switch open-circuit state, or lost software calibration data (less common, 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 other accompanying SRS communication fault codes.
  • 2
    Physical connection check: Locate the PAD switch (Song MAX/Yuan EV: usually on the right side of the glovebox; Tang/Qin: on the right side of the center console). 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 battery negative terminal and wait at least 90 seconds for the system capacitors to discharge (to prevent accidental airbag deployment). Unplug the switch connector and inspect the terminals for oxidation, backing out, or enlarged sockets. Clean the terminals with electrical contact cleaner and inspect the wiring harness outer sheath for abrasion marks.
  • 4
    Switch function test: Remove the switch and use a multimeter to measure resistance in the ON and OFF positions. Compare the readings with the repair manual specifications (typically 2.0-2.5 kΩ for ON, 4.5-5.0 kΩ for OFF, tolerance ±5%). Verify normal switch operating torque and check 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 (typically under the center console or floor center). Inspect specifically for interference points at the instrument panel frame.
  • 6
    ECU and calibration verification: If the 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 setting in the vehicle configuration code (VIN configuration). Replace the ECU and perform online programming if necessary.
  • 7
    System verification and testing: After reconnecting, turn the ignition switch to the ON position. Confirm the instrument cluster airbag warning light turns off after the self-check (about 6 seconds). Use the diagnostic tool to read the data stream. Operate the switch and verify the 'Passenger Airbag Cutoff Switch' status toggles between 'Enabled' and 'Disabled'. Finally, perform 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 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.