AU
B1695

In the BYD SRS (airbag) system, DTC B1695 indicates a front passenger Occupant Classification System (OCS) fault, rather than the literal "power supply voltage too high" — Qin Plus

Safety System

In the BYD SRS (airbag) system, DTC B1695 indicates a front passenger Occupant Classification System (OCS) fault, rather than the literal "power supply voltage too high".

This DTC indicates the SRS ECU detected an abnormal front passenger seat occupancy sensor signal, a communication interruption, or calibration data outside the valid range.

The OCS uses a piezoelectric sensor mat to detect front passenger seat occupancy and occupant weight category to control airbag deployment and staged inflation force.

If sensor resistance drifts, signal voltage is abnormal (standard no-load value is 1.2-1.5V), the communication circuit opens, or system calibration is incorrect, the SRS ECU triggers DTC B1695 and illuminates the airbag warning lamp.

This creates a serious safety risk, as the front passenger airbag may deploy incorrectly or fail to deploy during a collision.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1OCS sensor body aging, internal piezoelectric film fracture, or moisture ingress causes resistance drift (normal: 2.3-2.7kΩ) or abnormal output voltage.
  • 2Under-seat wiring harness connector oxidation or water ingress (especially in high-humidity southern environments), terminal back-out, or a broken locking clip causing intermittent poor contact.
  • 3Vehicle modifications (such as installing leather seat covers or replacing seat foam) or accident repairs deform the sensor mounting bracket, causing abnormal contact between the sensor and seat foam (gap must be <2mm).
  • 4OCS system calibration data lost after extended vehicle parking or battery disconnection; zero-point and full-scale calibrations not performed.
  • 5Front passenger seat slide rail interferes with the wiring harness, or a foreign object under the seat presses on the sensor mat, causing continuous abnormal force.
What To Do
  • 1
    Use a BYD VDS or Launch X-431 diagnostic tool to access the SRS system. Read the DTC B1695 freeze frame and live data stream to check if the sensor no-load voltage (normal: 1.2-1.5V) and load change rate are abnormal.
  • 2
    Remove and inspect the OCS module connector under the front passenger seat. Check the pins for oxidation or copper corrosion (commonly green), and measure the sensor resistance. Check the wiring harness for interference with the seat slide rail and verify the connector locking mechanism is intact.
  • 3
    Inspect seat structural integrity. Confirm the sensor mounting bracket is not deformed and verify there are no foreign objects or excessive compression between the sensor mat and the foam. If necessary, remove the seat for visual inspection.
  • 4
    If the hardware check is normal, perform the "Seat Occupant Detection System Calibration" procedure: keep the doors closed, sequentially simulate three states—unloaded (0kg), half load (approx. 30kg), and full load (approx. 75kg)—and wait for the diagnostic tool to indicate successful calibration.
  • 5
    If calibration fails or sensor resistance/voltage remains abnormal, replace the front passenger seat occupancy detection sensor assembly with an OEM part (verify the part number matches, e.g., SAS-3636100 or S6DM-3636100). Repeat the calibration procedure after replacement.
  • 6
    Clear the fault code and perform static and dynamic tests, including tapping the seat, adjusting the seat track, and driving on a bumpy road. Verify the fault light remains off and the data stream is normal.
Real-World Cases
BYD DTC AI Analysis

Song Pro DM oxidised connector caused signal drift

✓
Vehicle: BYD Song Pro DM (2019) Symptoms: SRS warning light stays permanently illuminated on the dashboard; front passenger seat occupancy indicator shows occupied when the seat is empty. Diagnosis: Scanned DTC B1695. Found severe oxidation (green corrosion) on the OCS module connector pins. Measured sensor resistance at 4.8kΩ (out of specification). Resolution: Cleaning the connector and applying conductive grease did not clear the fault. Replaced the front passenger seat occupancy sensor assembly (SAS-3636100), performed programming and calibration, and resolved the fault.
Original source ↗
BYD DTC AI Analysis

Qin Plus EV sensor pad piezoelectric film fractured

✓
Vehicle: BYD Qin Plus EV (2021). Symptoms: Airbag light came on suddenly while driving. Cleared the code, but the fault returned. Placing heavy objects on the passenger seat did not show occupancy. Diagnosis: DTC B1695-00. Swapped in a same-model seat to test — the fault moved with the seat. Disassembly found the piezoelectric film inside the sensor mat had fractured. Solution: Replaced the passenger seat cushion assembly (including occupancy sensor). Ran the three-state calibration (0kg/30kg/75kg). System returned to normal.
Original source ↗
BYD DTC AI Analysis

Tang DM-i connector clip broken causing intermittent fault

✓
Vehicle: BYD Tang DM-i (2022). Symptom: Airbag warning light came on 3 months after delivery, frequently recurred on bumpy roads. Diagnosis: B1695 communication fault (intermittent). Found broken locking tab on the 4-pin OCS module connector; signal intermittent when wiggling the wiring harness. Fix: Replaced seat harness connector (soldered an aviation connector as a replacement), resecured harness to prevent interference with seat rails. No recurrence after 500 km.
Original source ↗
BYD DTC AI Analysis

Yuan Pro sensor aging beyond calibration range

✓
Vehicle: BYD Yuan Pro (2020). Symptoms: Airbag light flashed then stayed on; no accident history. Diagnosis: B1695 out of calibration range; live data showed no-load voltage 2.1V (normal 1.2–1.5V). The sensor's internal piezoresistive resistor had aged due to high temperature and humidity. Resolution: Replaced the OEM sensor (S6DM-3636100), performed zero-point and full-scale calibration; no-load voltage returned to 1.35V.
Original source ↗
BYD DTC AI Analysis

Surui seat modification caused bracket deformation

✓
Vehicle: BYD Surui (2018 model). Symptoms: Airbag warning light on, OBD test not passed during annual inspection, could not clear fault codes. Diagnosis: B1695 Occupant Classification System fault. Found the OCS module mounting bracket had deformed from previous seat modifications, causing abnormal sensor loading and a 30% deviation in the weight recognition threshold. Fix: Repaired the sensor mounting bracket to ensure proper fit, used the Autel MS906 to perform the seat occupant sensor learning procedure (kept the seat unoccupied with doors closed for approximately 3 minutes), then cleared the fault once it became historical.
Original source ↗
Other Qin Plus 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.