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) — Atto 3

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.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Installing a non-genuine or incorrect-specification wheel speed sensor (e.g., mismatched supplier code, polarity, or tooth count) results in a hardware ID mismatch with the IPB software calibration.
  • 2The IPB control module software version does not match the vehicle configuration (e.g., failing to perform online configuration or VIN writing after replacing the IPB module with one from another model).
  • 3An intermittent short or open circuit in the front left wheel speed sensor wiring harness, or oxidized or backed-out connector pins, alters signal transmission characteristics and causes the system to misidentify the sensor type.
  • 4Tyre specification changes (e.g., fitting different size tyres or tone rings) cause the wheel speed signal frequency 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 C055600 (right front) or other wheel speed sensor fault codes are present. Check the vehicle speed, wheel speed values, and system voltage in the freeze frame data.
  • 2
    Inspect the appearance and installation condition of the left front wheel speed sensor. Verify the sensor tip has no 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 the specific 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 left front wheel with the vehicle stationary, verify the signal waveform amplitude and frequency are normal, and check for signal loss or abnormal jumps.
  • 5
    Perform 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. Perform 'Configuration Reset' or 'Online Matching' if necessary.
  • 6
    If the sensor or IPB module was replaced, perform 'Sensor ID Learning' or 'ECU Reprogramming' to ensure the IPB correctly recognizes the sensor hardware code.
  • 7
    If the above checks are normal, replace the left front wheel speed sensor with a genuine part (verify the part number: e.g., 5A-3630100 series). Clear the fault code, road test the vehicle, and observe if the fault recurs.
  • 8
    If the fault persists, test 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

✓
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

✓
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

✓
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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.