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) — Seal U

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 Seal U indicates a communication failure between the airbag control unit and the passenger airbag cutoff switch (PAD), usually due to a loose connector or internal switch fault. This triggers the airbag warning light and may disable the front passenger airbag. Severity is medium. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Switch connector loose or disconnected: Commonly occurs after removing and installing the dashboard, replacing the cabin air filter, repairing the center console, or retrofitting a large display. This results from technicians failing to securely reconnect the PAD switch plug, or a broken locking tab 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 to exceed the ECU recognition range (typically ±5% tolerance), especially on vehicles operating in high-humidity areas.
  • 3Wiring harness open or short circuit: Sharp frame edges, rodent damage, or pinching 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 mounting location: The switch fails to seat fully into the mounting base, keeping the internal sliding contact out of 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 causes the ECU to incorrectly detect a switch open-circuit state, or loss of software calibration data (less common, usually accompanied by other SRS fault codes).
What To Do
  • 1
    Diagnostic tool deep scan: Use VDS2000 or a BYD dedicated diagnostic tool to read 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: right side of the center console). Visually verify the connector is fully inserted. Confirm the locking mechanism (CPA lock) is intact. 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 to discharge the system capacitors (prevents accidental airbag deployment). Unplug the switch connector and inspect the terminals for oxidation, backing out, or spreading. Clean the terminals with electrical contact cleaner and inspect the wiring harness insulation for abrasion marks.
  • 4
    Switch function test: Remove the switch and use a multimeter to measure the resistance in the ON and OFF positions. Compare the readings with the repair manual specifications (typically 2.0-2.5 kΩ in the ON position, 4.5-5.0 kΩ in the OFF position, tolerance ±5%). Verify normal switch operating torque and inspect for binding.
  • 5
    Circuit continuity and insulation test: Use a multimeter to measure signal wire continuity (resistance <1Ω) between the switch connector and the SRS ECU connector (usually located under the centre console or floor centre). Measure insulation to ground and power (>10MΩ). Focus inspection on 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 in the vehicle configuration code (VIN configuration). If necessary, replace the ECU and perform online programming.
  • 7
    System verification and testing: After restoring connections, turn the ignition switch to ON. Confirm the instrument cluster airbag warning light turns off after the self-check (about 6 seconds). Read the data stream using the diagnostic tool. 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 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.