AU
B170F-00

DTC B170F-00 indicates a short to power fault in the driver seat Occupant Sensing System (OSS) — Atto 8

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 — Atto 8
  • 1Damaged seat occupancy sensor harness insulation causes a short to the power wire, commonly due to the seat fore-aft adjustment rail rubbing against the harness.
  • 2Water ingress, oxidation, or misaligned pins in the under-seat wiring harness connector (usually 4-pin) cause a short circuit between the power pin (PIN1/12V) and the signal pin (PIN2).
  • 3Fault in the seat occupancy sensor internal pressure sensing mat or control module circuit (such as protection capacitor breakdown or voltage regulator chip damage) causing a short circuit to power.
  • 4Water intrusion under the seat during wading or car washing causes an internal short circuit in the sensor control module (located on the inner side of the seat slide rail or under the seat).
  • 5Installation of a non-OEM seat or aftermarket sensor with a resistance that does not match the original specification (normally 2.5-3.5 kΩ), causing abnormal signal voltage.
What To Do
  • 1
    Connect a BYD VDS or 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's 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 use a multimeter to measure the sensor resistance. Normal value: 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. Specifically check for interference between the wiring harness and the metal 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 vehicle model, e.g., HA-XXXXXX for Song Plus; verify the part version 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. Confirm the Occupant Status in the diagnostic tool data stream changes normally (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 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.