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 3

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 3
  • 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 oxidized terminals interrupt 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 on rough roads.
  • 3Sensor body damage: Water ingress (wading repair), aging, or heavy loads cause abnormal internal resistance in the seat pressure sensor, preventing it from outputting the normal 0.5-4.5V pressure signal.
  • 4Configuration data missing or mismatched: After installing a used seat, upgrading from a low-spec 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 5V reference voltage supply to the sensors, or CAN communication line interference occurs.
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 300-500 Ω (static) or changes dynamically with pressure. Measure the supply voltage; it must be 5 V ± 0.25 V. Verify the signal wire voltage varies between 0.5-4.5 V with pressure. Verify the wiring harness insulation to ground is greater than 1 MΩ.
  • 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. Route the harness away from seat slide rails and sharp metal edges, leaving 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 driver/passenger side and high/low trim models). After replacement, leave the seat unoccupied for at least 10 minutes to perform adaptation.
  • 6
    If the fault code persists after replacing the seat or sensor, use the VDS2000 to execute 'Special Functions' → 'Seat Sensor Configuration' or 'Seat Sensor Calibration'. Enter the VIN to perform online programming and learning. On some F3 models, also execute '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 lamp remains off and the data stream shows a 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 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.