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 8

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 8
  • 1IPB module internal solenoid valve coil fault: open circuit, short circuit, or resistance drift (normal range typically 20-60 Ω, depending on model), causing abnormal drive circuit detection.
  • 2Valve spool mechanically stuck: Prolonged failure to replace brake fluid causes impurity deposits and poor valve spool lubrication, or abnormal brake fluid viscosity in low temperatures slows valve spool movement.
  • 3Control circuit board fault: The solenoid valve driver chip (MOSFET or dedicated driver IC) on the IPB internal PCB failed due to overheating, or has cold or broken solder joints.
  • 4Wiring harness and connector issues: Poor sealing of the IPB assembly plug (usually 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 solenoid valve metal components, or using 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-prefix 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 12V battery negative terminal and 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, ignition power) and ground pins, and the CAN line voltages (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V). Inspect the Valve A drive circuit for abnormal resistance.
  • 3
    Active test and function verification: Connect the diagnostic tool and perform the 'solenoid valve actuation test'. Listen for an operating 'click' from TCS valve A. Compare the sound to the other valves. If the sound is absent or weak, the valve is not operating. Observe the drive current waveform using an oscilloscope. The normal waveform is a square-wave pulse. If the current is 0 or remains continuously high, this confirms a circuit fault.
  • 4
    Hydraulic system inspection: Check the brake fluid level and colour. Test the fluid using a brake fluid moisture tester. If the moisture content is >3% or the colour is cloudy, completely replace the brake fluid with DOT4 standard brake fluid and perform the IPB bleeding procedure (use the diagnostic tool to execute the 'Hydraulic Unit Bleeding' mode).
  • 5
    Assembly replacement and matching: If diagnostics confirm an internal IPB fault, replace the IPB electro-hydraulic module assembly including the ECU (the spare part number must match the vehicle configuration). After installation, perform: ① coding; ② longitudinal/lateral acceleration sensor calibration; ③ wheel speed sensor signal verification; ④ road test to verify TCS function (test launch slip control on a low-adhesion surface such as wet tiles).
  • 6
    Repair confirmation: Clear the fault codes. Perform a mixed-condition road test of at least 5 km, including low-speed braking, emergency braking, and cornering. Read the fault codes again to confirm C000100 does not recur 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 8 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.