AU
B2AB573

This DTC indicates an abnormal driver seat fore-aft position sensor signal or a Seat Control Unit (SCU) communication fault — Atto 8

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.

The B2AB573 fault code on the Atto 8 indicates an abnormal driver seat fore-aft position sensor signal or a Seat Control Unit communication fault. Severity is medium, as it can disable seat memory and easy entry/exit functions. Common causes include a corroded or loose under-seat connector, or a faulty seat position sensor. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Oxidation, looseness, or pin corrosion (green corrosion) in the under-seat wiring harness connector, interrupting signal transmission or causing excessive resistance.
  • 2Faulty longitudinal position sensor (internal wiper wear, Hall element failure, or open resistor), causing the signal at a specific position to jump or remain fixed.
  • 3Jammed seat rail, ingress of foreign objects (such as coins), or insufficient lubrication, causing excessive wear of the sensor mechanical structure, stalling, or motor overload.
  • 4Seat Control Module (SCU) internal driver chip damaged or abnormal supply voltage (battery voltage below 11.5V causing signal distortion)
  • 5Poor connection caused by pulling the wiring harness, breaking the connector latch, or failing to fully engage the 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, confirm if B2AB573 is a current code, and review 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 under-seat wiring harness connector (usually located at the front or side of the seat rail) for oxidation, verdigris, looseness, or pin corrosion. If necessary, clean the connector and apply conductive grease.
  • 4
    Disconnect the sensor connector. Measure the supply voltage (5V reference) and verify the ground. Measure the sensor resistance (potentiometer type: 2-3kΩ, changing continuously with seat movement) or the signal voltage (Hall type).
  • 5
    Check the seat rails for foreign objects, deformation, or insufficient lubrication. Clean the rails and apply the 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 the wiring harness or connector is damaged, repair the wiring harness and replace damaged connector retaining clips. Secure the connection with cable ties to prevent poor contact.
  • 8
    Perform seat memory system calibration: Use the diagnostic tool to access Special Functions → Seat Memory Calibration → Follow the prompts to move the seat to the full forward and full rear limit positions to complete self-learning and save the position data.
  • 9
    Clear the fault code and 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 start-up), and the reverse-linked door mirror 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 Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.