AU
C055500

This DTC indicates the IPB (Intelligent Integrated Braking System) control module detects a mismatch between the front left wheel speed sensor hardware identifier (HW ID) or signal characteristics and the vehicle configuration parameters (EPC/calibration data) — Seal U

Braking System

This DTC indicates the IPB (Intelligent Integrated Braking System) control module detects a mismatch between the front left wheel speed sensor hardware identifier (HW ID) or signal characteristics and the vehicle configuration parameters (EPC/calibration data).

Specifically, when reading the wheel speed sensor ID code, resistance characteristics, or signal waveform parameters via the LIN bus or dedicated wiring harness, the IPB module detects a deviation between the actual characteristic values and the expected theoretical values.

This typically occurs when installing non-genuine parts, failing to reconfigure the system after a software upgrade, or when strong electromagnetic interference distorts the sensor signal characteristics.

This fault limits or disables the ABS, ESC, EBD (Electronic Brakeforce Distribution), and Automatic Emergency Braking (AEB) functions, severely impacting the vehicle's active safety performance, but does not directly cause mechanical brake failure.

The C055500 fault code on the Seal U indicates a mismatch between the front left wheel speed sensor’s hardware ID or signal and the vehicle’s braking system calibration. Severity is medium because ABS, ESC, EBD, and AEB may be limited or disabled, though normal braking is not directly failed. Common causes include an incorrect or non-genuine wheel speed sensor, or unmatched IPB module software/configuration. Visit an authorised dealer for diagnosis and reconfiguration or sensor replacement. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Installing a non-genuine or incorrect specification wheel speed sensor (e.g., mismatched supplier code, polarity, or tooth count) causes a mismatch between the hardware ID and the IPB software calibration.
  • 2IPB control module software version does not match the vehicle configuration (e.g., failing to perform online configuration or write the VIN after installing an IPB module from another model).
  • 3Intermittent short or open circuit in the left front wheel speed sensor wiring harness, or oxidized or backed-out connector pins, altering signal transmission characteristics and causing the system to falsely detect an incorrect sensor type.
  • 4Tyre specification changes (such as installing different size tyres or tone rings) cause the wheel speed signal frequency range to exceed the calibrated threshold, triggering the software protection mechanism.
  • 5Corrupted internal EEPROM data in the IPB control module or flashing failure causes lost or incorrect stored sensor configuration parameters.
What To Do
  • 1
    Use the VDS2000/BYD dedicated diagnostic tool to read all DTCs. Confirm if DTC C055600 (right front) or other wheel speed sensor fault codes are present, and check the vehicle speed, wheel speed values, and system voltage in the freeze frame data.
  • 2
    Check the appearance and installation condition of the left front wheel speed sensor. Verify the sensor head is free of oil contamination, the tone ring has no deformation or missing teeth, the connector shows no oxidation, backed-out pins, or signs of water ingress, and the wiring harness has no chafing or short to ground.
  • 3
    Disconnect the sensor connector and measure the sensor supply voltage (12V or 5V, depending on sensor type), ground wire resistance (<1Ω), and signal wire insulation to ground to rule out wiring faults.
  • 4
    Use an oscilloscope or diagnostic tool data stream to compare the four wheel speed signals: rotate the front left wheel while the vehicle is stationary, verify normal signal waveform amplitude and frequency, and check for signal loss or abnormal spikes.
  • 5
    Perform the IPB system configuration check: enter 'Special Functions' on the diagnostic tool and verify the vehicle VIN and tyre specification parameters (PCD, tooth count, rolling radius) match the actual vehicle. If necessary, perform 'Configuration Reset' or 'Online Matching'.
  • 6
    After replacing the sensor or IPB module, perform 'Sensor ID Learning' or 'ECU Reprogramming' to ensure the IPB correctly identifies the sensor hardware code.
  • 7
    If the above checks are normal, replace the left front wheel speed sensor with an OEM part (verify the part number, e.g., 5A-3630100 series). Clear the fault code, road test the vehicle, and observe if the fault reoccurs.
  • 8
    If the fault persists, measure the continuity and insulation of the IPB module to sensor wiring harness. If necessary, replace the IPB control module assembly and perform system configuration.
Real-World Cases
BYD DTC AI Analysis

Model mismatch after aftermarket sensor replacement on Song PLUS DM-i

✓
A 2021 Song PLUS DM-i with 30,000 km displayed "Braking System Fault." Scan showed DTC C055500. History indicated recent left front wheel speed sensor replacement at an independent workshop. The replacement sensor was an aftermarket unit with mismatched part number; its output signal amplitude deviated 10% from OEM calibration. Installed OEM sensor (part number 5A-3630100), performed IPB system "Wheel Speed Sensor Calibration," and cleared the fault.
BYD DTC AI Analysis

Configuration lost after IPB software update

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After the vehicle came in for routine servicing, the technician performed an IPB system software upgrade (OTA or via diagnostic tool). Following completion, the ABS warning light came on. The technician retrieved fault codes C055500 and C055600. Inspection revealed the upgrade process had been interrupted, corrupting the ECU configuration data. Using the VDS2000, the technician executed the 'online configuration' function to rewrite the vehicle VIN, tire specifications, and other parameters. After clearing the fault codes and conducting a road test, all four wheel speed signals synchronized normally and the fault resolved.
BYD DTC AI Analysis

Aftermarket wheels caused erratic tone ring signal

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Owner fitted larger wheels (19-inch to 21-inch) and a non-OEM tone ring, causing an ESC fault while driving. The scanner showed C055500. Live data showed intermittent fluctuation in left front wheel speed at 40 km/h. The modified tone ring has 48 teeth versus the original 45, pushing wheel speed frequency beyond the IPB calibration range. The fault cleared after restoring the original tone ring or modifying the 'tire rolling radius parameter' using a scanner (requires manufacturer authorization to alter calibration data).
BYD DTC AI Analysis

Backed-out pin in wiring harness causing intermittent type error

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ABS light illuminated intermittently when driving on rough roads. Fault disappeared during static inspection. Retrieved historical DTC C055500. Inspected left front wheel speed sensor connector and found terminal 2 (signal wire) on harness side slightly backed out, causing increased contact resistance (measured 3.5Ω, normal <0.5Ω). Re-crimped terminal, applied conductive grease and fitted waterproof boot. Cleared DTCs and road-tested repeatedly; fault did not reoccur.
BYD DTC AI Analysis

Internal fault in IPB control module

✓
No prior repairs. Sudden brake system fault. Scan tool showed C055500. Left front wheel speed sensor power and signal circuits normal. Swapped sensor with another wheel; fault persisted. Measured input impedance at IPB module pins: signal input internal resistance only 2 kΩ (normal >10 kΩ). Replaced IPB integrated brake assembly, bled brakes, and ran system configuration. Fault eliminated.
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.