AU
B1696

For the BYD SRS (Supplemental Restraint System/airbag system), DTC B1696 indicates a fault in the Seat Occupancy Sensor or its related circuit, not hardware damage to the SRS ECU itself — Atto 8

Safety System

For the BYD SRS (Supplemental Restraint System/airbag system), DTC B1696 indicates a fault in the Seat Occupancy Sensor or its related circuit, not hardware damage to the SRS ECU itself.

This sensor mounts inside or underneath the driver or front passenger seat.

It detects seat occupancy and classifies occupant weight, serving as a key input signal for the airbag deployment logic.

When the ECU detects an open circuit, short circuit, abnormal signal, or communication failure in the sensor circuit, it illuminates the airbag warning lamp.

The system may default to disabling the corresponding airbag and illuminate the 'airbag off' indicator.

This severely compromises occupant protection during a collision.

On some models, failing to perform the online configuration learning procedure after replacing the seat or sensor also triggers this code.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Seat occupancy sensor wiring harness connector loose, oxidized, or making poor contact: Frequent fore-and-aft seat adjustment or cleaning loosens the yellow connector (usually 4-pin), and terminal oxidation interrupts the signal.
  • 2Seat wiring harness mechanical damage: Seat frame edges or slide rails wear through the wiring harness insulation over time, causing a signal wire short to ground or open circuit, especially during water fording or driving on rough roads.
  • 3Sensor body damaged: Water ingress (wading repair), aging, or heavy loading causes abnormal internal resistance in the internal seat pressure sensor, preventing it from outputting the normal 0.5-4.5V pressure signal.
  • 4Configuration data lost or mismatched: After installing a salvaged seat, upgrading to a high-spec seat, or performing accident repairs, the sensor hardware part number does not match the vehicle configuration, or the 'seat sensor calibration' learning is incomplete.
  • 5Abnormal SRS ECU power supply/communication: In very rare cases, an internal ECU power module fault prevents the ECU from supplying the 5V reference voltage to the sensors, or interference affects the CAN communication lines.
What To Do
  • 1
    Use the BYD VDS or Launch X-431 diagnostic tool to read the complete fault codes and freeze frame data. Confirm whether the fault is on the driver or passenger side. Check if the 'seat occupancy status' in the data stream changes when applying pressure.
  • 2
    Visually inspect the yellow wiring harness connector under the affected seat (usually marked 'SRS' or 'Airbag'). Check for looseness, water ingress, pin oxidation, or corrosion. Clean with electrical contact cleaner and re-secure.
  • 3
    Disconnect the connector and measure the sensor resistance: the normal value is approximately 300-500Ω (static) or changes dynamically with pressure. Measure the supply voltage: it must be 5V ± 0.25V. Verify the signal wire voltage varies between 0.5-4.5V with pressure. Check the wiring harness insulation to ground; it must be greater than 1MΩ.
  • 4
    If the wiring harness is damaged, repair the wire (solder and insulate with heat-shrink tubing). Reroute the wiring harness and secure it with cable ties and dedicated clips. Keep the harness clear of seat slide rails and sharp metal edges, and leave sufficient slack.
  • 5
    If the sensor is damaged (abnormal resistance or no voltage output), replace the seat occupancy sensor assembly with the corresponding part number (verify the driver/passenger side and high/low trim model). After replacement, keep the seat unoccupied for more than 10 minutes to perform self-adaptation.
  • 6
    If the fault code persists after replacing the seat or sensor, use VDS2000 to execute 'Special Functions' → 'Seat Sensor Configuration' or 'Seat Sensor Calibration'. Enter the VIN to perform online programming and learning. Some F3 models also require executing 'Airbag System Configuration Write'.
  • 7
    Clear the fault code and perform a road test, including driving on bumpy roads and adjusting the seat forward and backward. Verify the fault light does not illuminate and the data stream shows normal occupancy status.
Real-World Cases
BYD DTC AI Analysis

Oxidised seat connector on Song Pro DM causes intermittent SRS fault

✓
Symptoms: While driving, the dashboard suddenly displayed 'Please check SRS system'. The airbag warning light stayed on, and the issue occurred intermittently after adjusting the driver's seat position. Diagnosis: Read DTC B1696 (Driver seat occupancy recognition sensor circuit fault) using Launch X-431. Inspection found the yellow 4-pin harness connector under the driver's seat loose, with slightly oxidised terminals. Sensor resistance measured normal (approximately 300–500Ω varying with pressure), indicating signal interruption from poor contact. Solution: Cleaned the connector terminals with electronic cleaner, re-secured the connection, and applied conductive paste. Secured the harness with cable ties to prevent pulling during seat movement. Cleared the fault codes and test drove the vehicle. The warning light went out and did not recur after multiple seat adjustments.
Original source ↗
BYD DTC AI Analysis

Qin Plus DM-i front passenger seat wiring harness chafed, open circuit

✓
Symptoms: With a passenger in the front seat, the instrument cluster still showed the passenger seatbelt warning (unoccupied icon) and the passenger airbag remained off. The driver side functioned normally. Diagnosis: VDS diagnostic tool read code B1696 (Passenger Seat Occupancy Sensor Circuit Open). Removed the passenger seat and found the pressure sensor harness under the seat was rubbing against the seat frame edge since factory assembly, breaking the internal copper wires. Measured sensor supply voltage: normal (5V); signal wire output: 0V (should vary 0.5–4.5V with pressure). Resolution: Replaced the passenger seat occupancy sensor assembly (Part No.: SA-5820100), repaired the damaged harness (soldered and added insulation sleeving), and rerouted the harness to avoid sharp metal edges. After replacement, performed 'Seat Sensor Calibration' with the diagnostic tool. Fault resolved.
Original source ↗
BYD DTC AI Analysis

F3 sensor shorted due to water ingress after wading

✓
After water damage repairs, the airbag warning light remained illuminated. Clearing the code with a generic OBD tool resulted in the fault returning immediately upon restart. Diagnosis: A dedicated diagnostic tool read DTC B1696 (driver seat occupancy sensor short to ground). Inspection found the harness connector under the seat had water ingress and internal corrosion from the submersion, causing a short between pins. The pressure sensor inside the seat foam also showed abnormal internal resistance from moisture (measured at only 20 Ω, far below normal). Resolution: Replaced the seat occupancy sensor (part number: L3-5820100) and the harness connector (or thoroughly cleaned and dried the existing one). Waterproofed the harness with waterproof tape. After clearing the DTC, performed an 'airbag system configuration write' using the diagnostic tool (as some F3 models require the configuration code to be re-written after sensor replacement).
Original source ↗
BYD DTC AI Analysis

Tang DM seat configuration not learned after accident repair

✓
Symptoms: After accident repairs (driver's seat assembly replaced), the instrument cluster displayed an SRS warning on startup that a standard scan tool could not clear. Diagnosis: Retrieved DTC B1696 (seat occupancy sensor not configured/communication fault). Inspection found the replacement seat was a second-hand unit, and its occupancy sensor part number did not match the vehicle specification (base-model seat fitted to a high-specification vehicle). Live data showed: “Sensor Status: Not Learned.” Solution: Since the sensor hardware model matched but configuration data was missing, accessed the BYD VDS2000 diagnostic tool and navigated to Airbag System → Special Functions → Seat Sensor Configuration. Entered the vehicle VIN, and online programming completed automatically. If the hardware had been incompatible, the sensor would need to be replaced with one having the correct part number. After configuration, the fault code cleared automatically.
Original source ↗
BYD DTC AI Analysis

G6 intermittent wiring harness short circuit on bumpy roads

✓
Symptoms: The airbag warning light flashes intermittently when driving on rough roads, but operates normally on smooth surfaces with no other abnormalities. Diagnosis: Retrieved historic DTC B1696 (intermittent). Inspection beneath the seat revealed a detached wiring harness clip. The harness rubbed against a metal bracket during seat rail movement, damaging the insulation and causing the signal wire to intermittently short to ground. Simulating rough road conditions (shaking the harness) illuminated the warning light immediately. Resolution: Repaired the damaged harness (cut out the damaged section and re-spliced), rerouted the harness, and secured it to a non-moving area of the seat frame using dedicated harness clips. Ensured adequate harness slack for full forward and rearward seat adjustment. Cleared the DTC and road tested; the fault no longer occurs on rough roads.
Original source ↗
Other Atto 8 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.