AU
C000100

DTC C000100 indicates an electrical or mechanical fault in TCS (Traction Control System) Control Valve A inside the IPB (Integrated Power Brake) — Atto 3

Braking System

DTC C000100 indicates an electrical or mechanical fault in TCS (Traction Control System) Control Valve A inside the IPB (Integrated Power Brake).

In BYD e-Platform 3.0 and DM-i architectures, the IPB module integrates the ABS/ESP/TCS hydraulic unit and ECU into a single assembly.

Valve A is typically the TCS main control solenoid valve or the left front wheel changeover valve.

This fault occurs when the ECU detects an abnormal valve drive circuit (open circuit, short circuit, or overcurrent) or an abnormal valve spool position feedback signal (delayed response or sticking).

When triggered, the fault disables the TCS function and forces the vehicle into fail-safe mode.

The system may limit ABS function but typically retains basic hydraulic braking (unassisted or partially assisted).

Due to the integrated design of the hydraulic oil circuit and solenoid valve inside the IPB assembly, technicians typically replace rather than repair this component.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1IPB module internal solenoid valve coil fault: Coil open circuit, short circuit, or resistance drift (normal range is typically 20-60Ω, depending on specific model), resulting in abnormal drive circuit detection.
  • 2Valve spool mechanically stuck: Prolonged failure to replace brake fluid causes impurity buildup and poor valve spool lubrication, or abnormal brake fluid viscosity at low temperatures causes sluggish valve spool operation.
  • 3Control circuit board fault: Overheating damaged the solenoid valve driver chip (MOSFET or dedicated driver IC) on the IPB internal PCB, or solder joints are dry or broken.
  • 4Wiring harness and connector issues: Poor sealing of the IPB assembly connector (usually located on the top or side of the module) causes terminal oxidation or back-out, or a chassis impact breaks the internal wiring harness.
  • 5Brake fluid deterioration: Excessive water content (>3%) corrodes internal metal parts of the solenoid valve, or incorrect use of non-DOT4 brake fluid causes seals to swell and stick.
What To Do
  • 1
    Initial diagnosis: Use the BYD VDS diagnostic tool (VDS2000/3000) to read all fault codes. Check for accompanying C000104 (circuit control valve 1 fault), U-series communication faults, or other wheel speed sensor faults. Record vehicle speed, brake pedal status, and hydraulic pressure values from the freeze frame data.
  • 2
    Visual and wiring inspection: Disconnect the battery negative terminal. Inspect the IPB module for brake fluid leakage, especially at the joint between the motor and the valve body. Measure the voltage at the IPB connector power pins (constant power and ignition power), ground pins, and CAN lines (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V). Check the Valve A drive circuit for abnormal resistance.
  • 3
    Active test and functional verification: Connect the diagnostic tool and run the 'Solenoid Valve Actuation Test'. Listen for an actuation 'click' from TCS Valve A. Compare the sound with other valves. No sound or a weak sound indicates the valve is not actuating. Use an oscilloscope to observe the drive current waveform. The normal waveform is a square-wave pulse. A current of 0 or a continuous high level confirms a circuit fault.
  • 4
    Hydraulic system check: Check brake fluid level and colour. Test using a brake fluid moisture tester. If moisture content is >3% or the colour is cloudy, completely replace with DOT4 brake fluid and perform the IPB bleeding procedure (use the diagnostic tool to execute 'Hydraulic Unit Bleeding' mode).
  • 5
    Assembly replacement and matching: If diagnostics confirm an internal IPB fault, replace the IPB electro-hydraulic module assembly with ECU (match the spare part number to the vehicle configuration). After installation, perform: ① Coding configuration; ② Longitudinal/lateral acceleration sensor calibration; ③ Wheel speed sensor signal verification; ④ Road test to verify TCS function (test start-off slip control on low-adhesion surfaces such as wet, slippery tiles).
  • 6
    Repair confirmation: Clear the fault code. Perform a road test of at least 5 km under mixed driving conditions, including low-speed braking, emergency braking, and cornering. Read the fault codes again. Confirm C000100 does not return and the instrument cluster ESC/TCS warning light is off.
Real-World Cases
BYD DTC AI Analysis

2021 Song PLUS DM-i: TCS light on with hard brake pedal

✓
The vehicle had covered 30,000 km when the ESC and TCS warning lights illuminated constantly on the dashboard. Diagnostic scan retrieved DTCs C000100 (TCS Control Valve A Fault 1) and C000104 (Circuit Control Valve 1 Fault). Inspection revealed slight leakage at the IPB module connector, with green corrosion on pins 3 and 4 (valve A drive). Cleaned the connector and applied conductive grease, which temporarily cleared the fault, but it returned after three days. Disassembled the IPB and found overheating damage to the internal PCB driver chip. Replaced the IPB assembly and completely replaced the brake fluid to resolve the issue. Root cause was micro-leakage of brake fluid causing circuit corrosion.
BYD DTC AI Analysis

Han EV Genesis Edition: Intermittent brake system fault at low speeds

✓
ABS warning light illuminated intermittently at 20–40 km/h. Scan tool retrieved history DTC C000100. During static testing, valve A actuation sound was intermittent. Valve A coil resistance measured 45 Ω at ambient temperature (normal), but rose to 120 Ω after heating to 60 °C with a heat gun (thermal open circuit). Diagnosed as internal IPB solenoid coil thermal stability failure. As the IPB is a complete assembly, replaced the unit and performed sensor calibration and brake bleeding. Fault has not reoccurred.
BYD DTC AI Analysis

Tang DM-p TCS failure after off-roading

✓
After an off-road water crossing, the dashboard displayed "Check brake system" with DTC C000100. Inspection revealed mud and water splash marks at the IPB mounting location (left front chassis rail) and a deteriorated connector seal. Further testing found TCS valve A spool sticking, likely from sand and silt entering the valve body through the breather or contaminated brake fluid. Cleaning the IPB and replacing the brake fluid did not resolve the issue; replaced the IPB assembly. Advised the owner to regularly inspect the IPB connector seals and avoid direct high-pressure washing.
BYD DTC AI Analysis

New BYD Seal reported C000100 fault immediately upon delivery.

✓
During new vehicle PDI, the ESC warning light was on continuously with DTC C000100. The IPB wiring harness had been pinched during assembly, damaging the valve A drive wire insulation and causing a short to ground. Repaired the harness, secured the routing, cleared the fault code and repeatedly tested the TCS active intervention function – all normal. Assembly process issue; did not replace the IPB assembly.
BYD DTC AI Analysis

BYD Qin PLUS DM-i reported valve fault after brake fluid replacement

✓
DTC C000100 appeared after a brake fluid change at a non-authorised workshop. Inspection found the technician did not use a diagnostic tool to perform the IPB bleed procedure, instead bleeding manually by pumping the pedal. This allowed air into the valve body and caused valve A to stick due to an air lock. Ran the 'Hydraulic Unit Bleed' function on the VDS (automatically cycles solenoid valves to build pressure and bleed). Repeated three times. Fault code cleared automatically and function returned to normal.
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.