AU
B16A0

DTC B16A0 indicates a fault in the passenger-side Occupant Classification System (OCS) rather than a purely SRS_ECU hardware fault — Atto 3

Safety System

DTC B16A0 indicates a fault in the passenger-side Occupant Classification System (OCS) rather than a purely SRS_ECU hardware fault.

The system uses a pressure sensor matrix integrated into the front passenger seat cushion and the OCS control module to monitor front passenger seat occupancy and weight category (adult/child/empty) in real time, and sends commands to the SRS_ECU to suppress or allow airbag deployment.

The OCS sets DTC B16A0 when it detects an open circuit, short circuit, abnormal signal, or loss of calibration data in the sensor circuit.

This fault prevents the SRS_ECU from accurately determining the front passenger status, posing the following risks: 1) Unnecessary airbag deployment when the front passenger seat is empty, increasing repair costs; 2) Airbag suppression during a collision due to incorrectly identifying the passenger as a child, resulting in inadequate occupant protection; 3) Abnormal seat belt pretensioner operating logic.

The system uses a 5V reference voltage circuit and is extremely sensitive to changes in circuit resistance and connector contact resistance.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Seat occupancy sensor (OCS) wiring harness connector loose, oxidized, or corroded by water ingress, causing increased contact resistance or intermittent signal interruption.
  • 2Physical damage to the pressure sensor pad (pressure sensing film) inside the seat cushion, such as sharp object punctures, plastic deformation from prolonged heavy object pressure, or folding creases.
  • 3Seat adjustment slide rail interferes with the OCS wiring harness during movement, causing harness insulation wear, copper core breakage, or a short circuit.
  • 4OCS control module internal ADC conversion circuit fault or EEPROM calibration data loss (common after replacing the seat or airbag control module without performing the calibration procedure)
  • 5Previous removal or modification of the front passenger seat (such as installing seat covers or heating pads) altered the sensor load characteristics or strained the wiring harness.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault Confirmation: Use the BYD dedicated diagnostic tool (VDS2000) to read the DTC. Confirm B16A0 is the current fault code. Record freeze frame data (including vehicle speed, seat status signal voltage, etc. at the time of the fault).
  • 3
    Visual inspection: Remove the front passenger seat (if necessary). Carefully verify the yellow OCS connector under the seat is fully locked, check the pins for green oxidation, and inspect the corrugated wiring conduit for wear or damage at the seat slide rail.
  • 4
    Circuit measurement: Turn the ignition switch back to the ON position (do not start the vehicle). Measure the OCS sensor supply voltage (standard value: 4.9-5.1V) and signal voltage (approx. 2.0-2.5V with seat empty; 0.5-4.5V with occupant, varying by weight). Check circuit insulation to ground and power supply.
  • 5
    Component inspection: Remove the seat cushion trim cover and visually inspect the pressure sensor mat for cracks, creases, or signs of liquid damage. Press the sensor area with a finger and observe if the 'Passenger Seat Weight' value in the diagnostic tool data stream changes linearly with pressure.
  • 6
    Repair action: Based on the identified fault, clean oxidized pins (use electronic contact cleaner and conductive grease), repair the damaged wiring harness (solder and insulate with heat-shrink tubing), or replace the damaged sensor pad or OCS control module.
  • 7
    System calibration: After completing hardware repairs, perform the OCS calibration procedure. Use the diagnostic tool to navigate to 'SRS System → Special Functions → OCS Calibration'. Follow the prompts to sequentially place no load, a 36kg standard weight, and a 75kg standard weight to perform the three-point calibration. This ensures the system accurately identifies the 'empty seat', 'child', and 'adult' states.
  • 8
    Verification test: Clear the fault code and perform a road test (including bumpy roads). Confirm the fault light turns off and the seat status in the data stream changes correctly according to actual occupancy. Perform a simulated crash test (use the diagnostic tool to execute the crash output test) to confirm the front passenger airbag control logic is normal.
Real-World Cases
BYD DTC AI Analysis

Damaged seat occupancy sensor pad on BYD Qin Pro causing B16A0

✓
Symptoms: The airbag warning light on the instrument panel stayed on. The diagnostic tool retrieved fault code B16A0 and could not clear it. Diagnosis: Checked the OCS connector beneath the front passenger seat and found the plug loose. Measured sensor resistance; it fell outside the standard range of 95–105Ω. Removed and inspected the seat, and found the pressure sensor pad partially damaged from prolonged compression by the onboard charger. Solution: Replaced the front passenger seat occupancy sensor assembly (including the pressure sensing pad and OCS control module). Used the diagnostic tool to perform the OCS system calibration procedure: sequentially placed 0kg, 36kg, and 75kg standard weights for the system to learn. Cleared the fault codes and road tested the vehicle. The airbag warning light turned off, and the data stream showed accurate seat status recognition.
Original source ↗
BYD DTC AI Analysis

BYD Song MAX: Loose wiring harness after seat cleaning triggered B16A0

✓
Symptom: The airbag warning light came on suddenly while driving. The owner recalled recently removing the passenger seat for deep cleaning. Diagnosis: Retrieved DTC B16A0-00 (passenger side seat occupancy sensor circuit fault). Inspected the wiring harness beneath the seat and found the OCS module connector not fully seated (tugging during cleaning had left the latch unsecured). Checked live data: passenger seat status showed ‘Unoccupied’ even with an occupant in the seat. Solution: Re-seated the OCS module connector, making sure the latch locked fully with an audible click. Ran the ‘seat occupancy sensor calibration’ using a scan tool. After calibration, the system returned to normal. Cleared the fault code; the fault has not returned.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM: seat rails chafing the wiring harness causing intermittent B16A0

✓
Symptoms: Dashboard displays 'Please Check Airbag System' warning. Intermittent fault, occurring more frequently on rough roads. DTC: B16A0. Diagnosis: Scanned with VDS2000 and confirmed B16A0 current. Inspected passenger seat occupancy sensor wiring and found harness chafing at seat rails; damaged insulation exposed copper conductors, causing intermittent short. Verified OCS control module mounting secure with no pin corrosion. Simulated rough road conditions by shaking harness; DTC status toggled between current and history, confirming fault location. Repair: Repaired damaged wiring (soldered the break and applied double-layer heat shrink insulation). Added abrasion-resistant corrugated tubing for harness protection. Rerouted and secured harness above seat frame to prevent rail contact. Cleared DTC, performed OCS system calibration, and conducted multiple road tests to confirm fault eliminated.
Original source ↗
BYD DTC AI Analysis

BYD Han EV: Creased pressure sensor membrane on new vehicle caused B16A0

✓
Symptoms: Airbag warning light illuminated on the dashboard after three months of ownership. The scan tool showed DTC B16A0, with the passenger seat registering a fault whether occupied or empty. Diagnosis: Read the fault code as B16A0 - Occupant Classification System Fault. Inspected the OCS module beneath the seat; no external damage and the connector was secure. Checked the live data and found the sensor voltage signal was abnormal, stuck at 4.8V (saturated). Removed the seat and found obvious creasing on the pressure sensor film. The owner had placed a hard suitcase on the seat, which crushed the sensor during loading or unloading. Resolution: Replaced the passenger seat cushion assembly (incorporating the built-in occupant sensor; the sensor and cushion are integrated and cannot be replaced separately). After replacement, ran the OCS initialisation learning procedure using the scan tool. Following the workshop manual, placed 20kg weights (simulating empty seat/child threshold) then 60kg weights (simulating adult threshold) on the seat to perform the calibration test. Confirmed the system correctly distinguishes between the three states.
Original source ↗
BYD DTC AI Analysis

OCS connector pin oxidation fault on BYD e5 taxi

✓
Symptoms: On a BYD e5 taxi at 80,000 km, the airbag warning light illuminated. A diagnostic scan detected DTC B16A0. Diagnosis: Read DTC B16A0. Historical fault records showed five previous intermittent occurrences. Inspected the seat occupancy sensor connector and found obvious green oxidation on the pins (water ingress under the seat from frequent cleaning). Measured the sensor supply voltage: specification is 5 V reference, actual reading was 4.2 V with 0.3 V fluctuation, indicating excessive contact resistance in the harness. Further inspection found a loose intermediate connector between the OCS control module and the sensor. Resolution: Cleaned the oxidised connector pins with electronic contact cleaner. After drying, applied conductive grease to prevent re-oxidation. Re-tightened all connectors, ensuring contact resistance below 0.5 Ω. Cleared fault codes and completed a 20 km road test; the fault did not reappear. Advised the owner to avoid directing water under the seat when cleaning and to use a damp cloth instead of a pressure washer.
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.