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B169B

DTC B169B (usually with sub-code -00) indicates a range/performance fault or invalid signal in the driver seat horizontal position sensor (DSeat Horizontal Position Sensor) circuit — Seal U

Safety System

DTC B169B (usually with sub-code -00) indicates a range/performance fault or invalid signal in the driver seat horizontal position sensor (DSeat Horizontal Position Sensor) circuit.

This three-wire sensor (5V reference supply, signal ground, analog signal output) mounts on the driver seat slide rail to monitor the fore-and-aft seat position in real time (0-240 mm travel range).

The BCM or seat control module sets this DTC when it detects the sensor output voltage falls outside the calibrated range (normally 0.5-4.5V, changing linearly with position), an open or short circuit, or a value that remains unchanged for an extended period.

This fault directly affects the seat memory and welcome seat rearward movement functions.

It may also prevent the airbag system from optimizing pretensioner force based on seat position (linked with the SRS on some models).

This fault compromises user experience and vehicle safety.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose sensor plug or oxidized terminals: Frequent fore-and-aft seat movement fatigues the wiring harness. A loose 5-pin plug or copper corrosion on the terminals interrupts the signal (accounts for 80% of cases).
  • 2Water ingress and corrosion under the seat: Car wash fluid penetration, aged door seal leaks, or a blocked sunroof drain tube causes a short to ground in the sensor connector or wiring harness.
  • 3Wiring harness mechanical interference with slide rail: The wiring harness retaining clip between the seat slide rail and vehicle body detaches. During seat movement, the harness rubs against the metal slide rail, breaking the internal copper wires.
  • 4Physical damage to the sensor body: Vehicle accident impact or long-term wear dislodges or breaks the internal resistor wiper, causing an abnormal resistance value (infinite or non-linear).
  • 5Control module software mismatch: Version inconsistency after a BCM or seat control module upgrade causes sensor data parsing errors or communication timeouts (accompanied by U0146).
What To Do
  • 1
    Use VDS2000 or an equivalent diagnostic tool to read the fault code and data stream. Move the seat forward and backward. Observe if the 'Driver Seat Horizontal Position' value changes accordingly (normal range: 0-240 mm) to confirm the fault symptom.
  • 2
    Visually inspect the sensor connector under the seat (usually located in front of the left seat rail). Check the connector for looseness and the pins for oxidation (green copper corrosion). If necessary, clean with electrical contact cleaner and apply conductive grease. Fully seat the connector and secure it with a cable tie.
  • 3
    Disconnect the sensor connector. At the wiring harness side, verify the 5V reference voltage (approximately 5V to ground) and signal ground (0V to ground). Measure the signal wire insulation resistance to ground (>10MΩ) to rule out a short circuit.
  • 4
    Check the wiring harness routing. Inspect for detached retaining clips or chafing against the seat slide rail. Adjust the harness routing and install a rubber protective sleeve if necessary.
  • 5
    Check for water stains under the seat carpet and trace the leak source (focus on the door seals and sunroof drain holes). After repairing the leak, replace the damaged wiring harness grommet.
  • 6
    If the wiring is normal, remove the sensor and measure its internal resistance. The resistance must change linearly from the seat's foremost to rearmost position (typically 1.2kΩ–4.8kΩ). If the resistance is infinite or non-linear, replace the sensor (e.g., part number EA-6923100).
  • 7
    After replacing the sensor or repairing the wiring, perform the 'Seat Position Calibration' or 'Initialization' special function: write the sensor zero position (fully forward) and maximum travel (fully rearward) data, and reset seat memory positions 1/2/3.
  • 8
    For software issues, simultaneously update the BCM and seat control module to the latest compatible version, then perform module matching and position recalibration.
  • 9
    Clear the fault code. Perform over 20 seat fore/aft adjustment tests, memory function tests, and a bumpy road test. Verify the data stream shows no abnormal jumps.
Real-World Cases
BYD DTC AI Analysis

Han EV seat memory function inoperative (signal open circuit)

✓
After starting the vehicle, the instrument cluster displayed "Please check seat system" and the warning light remained on. The scan tool retrieved DTC B169B-00 (driver seat horizontal position sensor signal invalid). Live data showed the position value fixed at 0 mm with no change; the signal wire voltage at the sensor connector was constantly 0 V. Inspection revealed the 5-pin connector was loose and had oxidised pins. Cleaned the connector, applied conductive grease, secured the wiring harness, and performed seat position calibration. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Tang DM sensor physical damage after accident repair

✓
After front collision repairs, the instrument cluster kept showing a seat system fault (DTC B169B). The driver's seat wouldn't auto-return to the memory position, and the dash light flashed during adjustment. Sensor resistance was infinite. Disassembly revealed the internal resistance slider had derailed and fractured from the collision impact. Replaced the driver seat horizontal position sensor (part number: EA-6923100), performed seat position initialization and memory setting, and normal operation was restored.
Original source ↗
BYD DTC AI Analysis

Water ingress caused an intermittent fault in the Song Pro DM.

✓
DTC B169B stored intermittently after rain or car washing, with the seat memory function working sporadically and the warning lamp occasionally self-extinguishing. Inspection found water stains on the carpet beneath the seat and leaks from perished door seals. Pin 3 of the sensor connector was corroded, and the wiring harness insulation resistance measured only 0.3MΩ. Repaired the leaks, replaced the waterproof sealing boots, applied silicone grease for waterproofing, and adjusted the wiring harness routing, completely resolving the fault.
Original source ↗
BYD DTC AI Analysis

Software mismatch after Qin Plus system upgrade

✓
After the dealership upgraded the infotainment system, DTC B169B and U0146 (lost communication with seat control module) appeared. The seat adjustment buttons occasionally malfunctioned. Inspection revealed a software version mismatch between BCM V3.2.1 and seat control module V1.8.5, causing sensor data parsing errors. Upgraded the seat control module to V2.1.3, performed module matching, and recalibrated the seat position. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Yuan Plus wiring harness wear causing poor contact

✓
Seat warning light illuminates intermittently on rough roads, logging DTC B169B. Static inspection normal. Wiggling the seat harness caused the live data to instantly jump to 255. Found the harness clip between the seat rail and body detached, allowing the harness to rub against the rail and break 3 copper strands in the signal wire. Replaced the harness assembly, secured it with at least 2 cm clearance from the rail, and added a rubber protective sleeve. Fault resolved.
Original source ↗
Other Seal U 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.