AU
C000100

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

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.

The C000100 fault code on the Seal U indicates an electrical or mechanical fault in TCS Control Valve A inside the Integrated Power Brake module. Severity is medium because traction control is disabled and braking assistance may be limited, though basic braking usually remains. Common causes include a faulty internal solenoid valve coil or a mechanically stuck valve spool. The recommended fix is diagnosis by an authorised dealer, usually replacing the IPB module. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1IPB module internal solenoid valve coil fault: Coil open circuit, short circuit, or resistance drift (normal range is typically 20-60Ω, 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 at low temperatures causes sluggish valve spool movement.
  • 3Control circuit board fault: Overheating damage to the solenoid valve driver chip (MOSFET or dedicated driver IC) on the internal IPB PCB, or cold or broken solder joints.
  • 4Wiring harness and connector issues: Poor sealing of the IPB assembly connector (usually located on the top or side of the module) causing terminal oxidation or back-out, or chassis impact causing an internal wiring harness break.
  • 5Brake fluid deterioration: Excessive water content (>3%) corrodes internal metal parts of the solenoid valve, or using non-DOT4 brake fluid causes seal swelling and sticking.
What To Do
  • 1
    Initial diagnosis: Use the BYD VDS diagnostic tool (VDS2000/3000) to read all fault codes. Check for accompanying faults such as 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 battery negative terminal. Inspect the IPB module exterior for brake fluid leaks, especially at the joint between the motor and valve body. Measure the voltage at the IPB connector power pins (constant power, 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 resistance for abnormalities.
  • 3
    Active test and function verification: Connect the diagnostic tool and perform the 'solenoid valve actuation test'. Listen for an actuation 'click' from TCS valve A. Compare this with the sound of the other valves. No sound or a faint sound indicates the valve is not operating. 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, and 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 adaptation: If diagnostics confirm an internal IPB fault, replace the IPB electro-hydraulic module assembly with ECU (spare part number must match 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 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 turning. Read the fault codes again. Confirm C000100 does not return and the instrument cluster ESC/TCS warning lamp 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

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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

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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.

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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

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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 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.