AU
B2AB573

This DTC indicates an abnormal driver seat fore-aft position sensor signal or a Seat Control Unit (SCU) communication fault — Qin Plus

Thermal Management System

This DTC indicates an abnormal driver seat fore-aft position sensor signal or a Seat Control Unit (SCU) communication fault.

The ECU detects a sensor signal voltage outside the normal range (0.5-4.5V), an inconsistent signal, or a complete signal loss.

This disables the seat memory system and easy entry/exit functions.

Typically a Hall-effect or potentiometer type, the sensor mounts on the seat rail.

It monitors the seat fore-aft position in real time, providing position feedback to the memory function and intelligent cockpit system.

Although the fault message displays "start-up failure", a seat position signal failure actually prevents the related functions from starting.

4
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Oxidation, looseness, or pin corrosion (green corrosion) at the under-seat wiring harness connector, causing signal transmission interruption or excessive resistance.
  • 2Faulty longitudinal position sensor (internal wiper wear, Hall element failure, or open resistor), causing the signal to jump or remain fixed at a specific position.
  • 3Seat rail binding, foreign object (such as a coin) ingress, or insufficient lubrication causes excessive wear of the sensor mechanical structure, motor stall, or motor overload.
  • 4Damaged Seat Control Unit (SCU) internal driver chip or abnormal supply voltage (battery voltage below 11.5V causing signal distortion)
  • 5Poor connection caused by a pulled wiring harness, broken connector latch, or incompletely seated connector during vehicle modifications (such as installing seat ventilation/heating pads).
What To Do
  • 1
    Use VDS2000 or Launch X431 to read the Seat Control Module (SCU) fault codes, verify if B2AB573 is a current code, and check the freeze frame data for the seat status when the fault occurred.
  • 2
    Access the data stream and monitor the "Driver seat fore-aft position" value. Manually adjust the seat through its full range of travel and observe if the value changes linearly (normal values change continuously between 0-255mm or 0.5-4.5V, without jumps or fixed values).
  • 3
    Inspect the wiring harness connector under the seat (usually at the front or side of the seat rail) for oxidation, verdigris, loose connections, or pin corrosion. Clean and apply conductive grease if necessary.
  • 4
    Disconnect the sensor connector. Measure the supply voltage (5V reference) and verify the ground. Measure the sensor resistance (potentiometer type: normally 2-3kΩ, changing continuously with seat movement) or signal voltage (Hall type).
  • 5
    Check the seat rails for foreign objects, deformation, or insufficient lubrication. Clean the rails and apply specified grease. Verify the seat moves smoothly without binding.
  • 6
    If the sensor is damaged, replace the driver seat fore-aft position sensor (on some models, the sensor is integrated with the seat frame, requiring partial seat disassembly).
  • 7
    If you find damage to the wiring harness or connector, repair the wiring harness, replace damaged connector locking clips, and secure the connection with cable ties to prevent poor contact.
  • 8
    Perform seat memory system calibration: Use the diagnostic tool to enter Special Functions → Seat Memory Calibration. Follow the prompts to move the seat to the foremost and rearmost limit positions to complete self-learning and save the position data.
  • 9
    Clear the fault code. Verify normal operation of the seat memory 1/2/3 position storage and recall, the easy entry/exit function (seat moves back after power off / restores on startup), and the reverse mirror linkage function.
Real-World Cases
BYD DTC AI Analysis

Tang DM-i seat memory function completely failed

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Symptoms: Instrument cluster displayed "Please check seat system". Memory and easy entry/exit failed completely. Manual adjustment worked, but the system would not save positions. Diagnosis: SCU showed code B2AB573. Data stream showed longitudinal position fixed at 255 cm. Removed and inspected the sensor harness connector; found oxidation with green corrosion on the pins. Sensor measured open circuit. Solution: Cleaned the harness connector and applied conductive grease. Replaced the driver seat longitudinal position sensor. Performed seat memory system calibration (moved seat to full forward and rearward positions to complete learning). Cleared fault codes; functions restored.
BYD DTC AI Analysis

Han EV: Abnormal Seat Sliding / Seat Position Memory Malfunction

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Symptoms: After sitting overnight, the seat automatically moved forward against the steering wheel on startup. Saved memory positions recalled with 10–15cm deviation. Fault occasionally reported while driving. Diagnosis: Retrieved DTC B2AB573 (Range/Performance) accompanied by U01B487 (Communication). Found a foreign object (coin) jamming the rails. After clearing it, live data showed the position jumping from 20cm to 80cm. Determined the sensor’s internal slider had poor contact. Battery voltage also measured low at 11.2V. Solution: Replaced the driver seat longitudinal position sensor assembly and seat control module (SCU—as the stall condition likely overloaded the driver chip). Completed seat memory initialization and calibration. Recommend checking battery state of health.
BYD DTC AI Analysis

BYD Song PLUS DM-i Easy Entry/Exit function inoperative

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Symptoms: When shutting down and opening the door, the seat does not automatically move rearward (Easy Entry failed). Reverse mirror tilt functions normally. Manual adjustment occasionally stutters or jumps; the system will not save new memory positions. Diagnosis: Retrieved DTC B2AB573 (present in history and current). Freeze frame data showed the seat moving rearward when the fault occurred, with the signal suddenly dropping out. On-vehicle testing revealed the sensor value dropped to "0" (signal loss) when the seat reached a specific position (mid-to-rear). Resolution: Replaced the seat longitudinal position sensor (individual sensor, not the complete assembly). Checked the runner lubrication and applied grease. Reset the seat memory positions. Tested the Easy Entry function—now operating normally.
BYD DTC AI Analysis

Seal seat memory malfunction / simultaneous fault codes across multiple systems

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Symptoms: 3-month-old vehicle. Intermittent seat memory failure with inoperative lumbar support adjustment. During faults, fore-aft seat adjustment slowed and memory buttons were unresponsive. Diagnosis: SCU scan revealed DTCs B2AB573 (longitudinal position sensor) and B2AB673 (height position sensor) plus additional sensor faults. Inspection found the owner had disturbed the wiring harness while installing aftermarket seat ventilation/heating pads. The longitudinal position sensor connector was not fully seated due to a broken locking clip, causing poor contact; technicians measured high resistance on the signal line. Resolution: Re-secured the wiring harness connector and used cable ties to ensure reliable connection. Replaced the damaged connector locking clip. Cleared all DTCs and performed a full seat travel initialisation procedure. Cautioned the owner to protect the factory wiring harness during future modifications.
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.