AU
B170F-00

DTC B170F-00 indicates a short to power fault in the driver seat Occupant Sensing System (OSS) — Seal U

Safety System

DTC B170F-00 indicates a short to power fault in the driver seat Occupant Sensing System (OSS).

Integrated into the driver seat cushion, the sensor uses a pressure sensing mat and an electronic control module to detect seat occupancy.

It sends a 0.4-4.6V analog voltage signal to the SRS airbag control unit (approximately 0.5V when unoccupied and 4.2V when occupied).

The SRS module sets this DTC when it detects a continuous voltage above 4.8V or near battery voltage.

This occurs if the signal circuit shorts to the 12V power supply line (B+), the internal sensor circuit breaks down, or the control module fails.

This fault forces the SRS system into fail-safe mode: the driver airbag may fail to deploy, the seat belt reminder function may malfunction (false or missing warnings), and the instrument cluster airbag warning light remains illuminated.

Because this fault affects the passive safety system, do not drive the vehicle until repaired.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged seat occupancy sensor wiring harness insulation causes a short circuit to the power wire, commonly where the seat fore-and-aft adjustment rail chafes against the wiring harness.
  • 2Water ingress, oxidation, or misaligned pins in the under-seat wiring harness connector (usually 4-pin), causing a short circuit between the power pin (PIN1/12V) and signal pin (PIN2).
  • 3Internal fault in the seat occupancy sensor pressure sensing mat or control module circuit (e.g., protection capacitor breakdown or voltage regulator chip damage) causing a short to power.
  • 4Water entering under the seat during vehicle wading or washing causes an internal short circuit in the sensor control module (located on the inner side of the seat slide rail or at the seat bottom).
  • 5Installing a non-OEM seat or aftermarket sensor with a resistance specification (normally 2.5-3.5 kΩ) that does not match the original part, causing abnormal signal voltage.
What To Do
  • 1
    Connect the BYD VDS or a professional diagnostic tool such as Launch X-431 or Autel. Read the DTC to confirm B170F-00 is a current fault (Active) and record the freeze frame data (Fault Frame).
  • 2
    Visually inspect the wiring harness connector under the driver seat (black 4-pin connector) for looseness, backed-out terminals, water ingress, or corrosion. Measure the connector terminal voltages: power (PIN1) should be 12V, signal (PIN2) 0.4-4.6V, and ground (PIN4) 0V. If the signal wire voltage is 12V, confirm a short to power.
  • 3
    Disconnect the sensor connector and measure the sensor body resistance using a multimeter. The normal value is 2.5-3.5 kΩ. If the resistance is 0 or infinite, replace the sensor. If the resistance is normal, the fault is in the wiring harness.
  • 4
    Inspect the seat slide rails and wiring harness routing. Check for interference between the wiring harness and metal guide rails throughout the full fore-and-aft seat adjustment travel. Repair any damaged wires (soldering + heat-shrink tubing) and re-secure the wiring harness away from moving parts. Install corrugated conduit for protection if necessary.
  • 5
    If the wiring harness is normal, replace the driver seat occupancy sensor assembly (part numbers vary by model, e.g., HA-XXXXXX for Song Plus. Verify the part version number matches the VIN).
  • 6
    Use the diagnostic tool to perform 'Seat Occupancy Sensor Calibration' and 'SRS Configuration' to learn the occupied/unoccupied status thresholds.
  • 7
    Clear the fault code and verify functionality: simulate unoccupied (seat empty) and occupied (apply over 30kg of pressure) conditions, then confirm the Occupant Status in the diagnostic tool data stream changes correctly (UNOCCUPIED/OCCUPIED) and the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

After replacing seats with aftermarket units on a Song Plus DM-i, the airbag warning light stays on.

✓
After the owner replaced the driver's seat at a third-party workshop with a non-genuine unit, the airbag warning light stayed on and the driver's seatbelt reminder stopped working. VDS scan retrieved DTC B170F-00. Measured the occupancy sensor in the new seat: resistance only 0.8kΩ (OEM specification 2.5–3.5kΩ). The aftermarket sensor's incompatible spec caused abnormal signal voltage. Replaced the sensor with a genuine driver's seat occupancy sensor, then ran sensor calibration and SRS configuration writing. Fault codes cleared; system returned to normal.
Original source ↗
BYD DTC AI Analysis

Seat sensor short circuit in Qin Plus EV after water wading

✓
After driving through standing water approximately 30cm deep, the instrument cluster displayed 'Check Airbag System' and the driver's seat heating failed. Retrieved DTCs B170F-00 and U0151. Removed the seat and found water accumulation on the inner side of the seat rails, oxidation and corrosion on the occupancy sensor control module pins, and measured a short to ground on the signal wire. Replaced the seat occupancy sensor assembly, removed water from the seat foam and dried it, then applied waterproof sealant at the sensor mounting location. Performed system calibration after the repair. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Han EV seat adjustment causing wiring harness wear, resulting in intermittent fault

✓
While driving, the instrument cluster occasionally showed an airbag fault warning that cleared after stopping and restarting. The driver's seat belt reminder also worked intermittently. Stored DTCs revealed an intermittent B170F-00. Inspection found that the occupant sensor wiring harness rubbed against the seat rail during fore-aft adjustment, damaging the insulation and causing occasional shorting to the power wire. Repaired the damaged wiring (re-soldered and re-wrapped). Rerouted the harness and secured it to the seat frame. Fitted a wiring protection sleeve to prevent contact with moving parts. Two weeks of follow-up: no recurrence.
Original source ↗
BYD DTC AI Analysis

Sensor calibration data lost on new Tang DM-p

✓
One week after delivery of the new vehicle, it frequently triggered false 'person in vehicle' warnings after locking when unoccupied, or displayed 'no person in vehicle' when occupied. Read DTCs B170F-00 and B1710-00. Inspected sensor—no physical damage, but scan tool showed sensor output voltage fixed at 2.0 V (not changing with occupancy). Determined cause: severe vibration during transport or battery disconnection caused calibration data loss. Performed 'seat occupancy sensor zero-point calibration' and 'sensitivity learning' using scan tool. No parts replaced; fault resolved.
Original source ↗
BYD DTC AI Analysis

Destroyer 05 loose connector fault after service

✓
The airbag warning light came on after routine maintenance (including interior cleaning). The owner reported the seats had been removed during this service. We read DTC B170F-00. We checked the wiring harness under the seat and found the 4-pin occupancy sensor connector was not fully seated (locking tab not engaged). This caused poor contact at the signal pin and intermittent contact with the adjacent power pin. We reseated the connector, ensured the locking tab engaged, cleared the DTC, and tested the system with and without an occupant. The system returned to normal.
Original source ↗
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.