AU
C001C00

DTC C001C00 indicates the IPB (Intelligent Integrated Braking System) ECU detects a fault in the right rear wheel inlet valve (normally open valve) drive circuit — Seal U

Braking System

DTC C001C00 indicates the IPB (Intelligent Integrated Braking System) ECU detects a fault in the right rear wheel inlet valve (normally open valve) drive circuit.

This typically occurs when the internal ECU valve drive circuit (MOSFET or dedicated driver chip) detects an open circuit, short to power, short to ground, or abnormal current feedback while attempting to drive the right rear inlet valve.

The inlet valve acts as a key actuator in the ABS/ESP hydraulic control unit, controlling brake fluid flow from the master cylinder to the right rear wheel cylinder.

This fault prevents the right rear wheel from participating in ABS pressure regulation and ESP active braking intervention.

Extreme cases may affect braking balance; however, the system retains basic hydraulic braking functions (direct pedal pressure build-up).

The warning lamp illuminates, and the system disables functions including ABS, ESP, and Automatic Emergency Braking (AEB).

The C001C00 fault code on the Seal U indicates a medium-severity fault in the right rear wheel inlet valve drive circuit within the IPB braking system. Common causes include an open or shorted inlet valve solenoid coil, or a failed internal ECU driver chip or MOSFET. Basic braking should remain, but ABS, ESP, and AEB may be disabled. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Open or short circuit in the right rear inlet valve solenoid coil inside the IPB electro-hydraulic module (resistance outside the standard 3-7Ω range)
  • 2Hardware fault in the IPB ECU internal valve drive circuit, such as a damaged driver chip (e.g., L9369 or other dedicated IC) or MOSFET breakdown.
  • 3The IPB wiring harness connector (usually located on the top or side of the module) is loose, corroded by water ingress, or has oxidized pins, causing excessive contact resistance.
  • 4Contaminated and deteriorated brake fluid due to prolonged lack of replacement causes the inlet valve spool to mechanically bind. The resulting abnormal drive current triggers fault protection.
  • 5Unstable IPB module power supply voltage or poor ground connection causes the ECU to misjudge the valve drive status.
What To Do
  • 1
    Use a dedicated diagnostic tool (VDS or equivalent) to read the complete fault code and freeze frame data. Check for accompanying sub-codes such as C001C01 (right rear inlet valve short to power) or C001C02 (short to ground), and verify the hydraulic unit version number.
  • 2
    Visually inspect the IPB electro-hydraulic module exterior for leaks. Disconnect the battery negative terminal, then check the connector pins for corrosion, bending, or backing out. Measure the wiring harness continuity from the connector to the ECU.
  • 3
    Disconnect the IPB connector. Use a multimeter to measure the right rear inlet valve solenoid resistance (typically the terminal for pin RR-INLET). The standard value is 3-7 Ω. Compare this reading with the left rear wheel resistance (circuit for C001800). A deviation exceeding 2 Ω indicates a faulty valve body.
  • 4
    Connect the diagnostic tool and perform the 'Hydraulic Unit Actuator Test'. Listen for the right rear inlet valve operation sound. If other valves click but the right rear valve makes no sound, or if the drive current exceeds 1.5A or falls below 0.3A, confirm an internal fault.
  • 5
    Upon confirming an internal IPB fault, replace the complete IPB electro-hydraulic module assembly (BYD part numbers vary by model; for example, the Song PLUS DM-i typically uses the assembly with the ECU). Never disassemble or repair the hydraulic unit separately.
  • 6
    After installing the new IPB, use the diagnostic tool to execute the 'Bleeding Procedure' (access IPB special functions to perform motor pump bleeding and wheel cylinder bleeding). Bleed the system in the following sequence: right rear - left rear - right front - left front. Verify the lines are free of air locks.
  • 7
    Clear all fault codes and perform a road test to verify: at speeds exceeding 40 km/h, perform an emergency braking test to verify ABS operation; check the ESP OFF switch function; and confirm no warning lights illuminate on the instrument cluster.
Real-World Cases
BYD DTC AI Analysis

Open circuit in IPB internal solenoid valve coil caused ABS failure

✓
A 2021 Song PLUS DM-i at 30,000 km had constant ABS and ESP warning lights. VDS read fault code C001C00 (right rear inlet valve driver fault). Freeze frame showed 0 km/h vehicle speed at the time of the fault. The technician disconnected the IPB connector and measured the right rear inlet valve resistance at infinite (open circuit). The left rear inlet valve measured 5.2Ω (normal). This confirmed an open solenoid coil inside the IPB assembly. Replaced the IPB electro-hydraulic module assembly and performed the brake bleed procedure. Cleared the fault codes. ABS function returned to normal.
Original source ↗
BYD DTC AI Analysis

Connector corrosion after water ingress caused intermittent fault

✓
After driving through standing water, the dashboard intermittently displayed "Check Brake System" and DTC C001C00 set sporadically. The IPB wiring harness connector showed obvious water stains and green corrosion inside. Reduced insulation resistance between pins caused the ECU to misdiagnose an actuator fault. Cleaned the connector with electrical contact cleaner, dried it thoroughly, applied BYD conductive grease (or petroleum jelly), and repositioned the waterproof seal. No recurrence after one week of continuous monitoring following reassembly.
BYD DTC AI Analysis

Brake fluid contamination caused valve body sticking and false fault codes

✓
During maintenance, found severely degraded brake fluid (black, water content >4%). ABS warning light then lit up. Read DTC C001C00. Solenoid resistance measured normal, but actuation test showed drive current fluctuating abnormally (0.8A-1.2A unstable; normal is stable ~1.0A). Disassembled IPB for inspection (teaching demo) and found brown deposits jamming the inlet valve spool. IPB is a sealed assembly, so replaced the IPB module and brake fluid. Fault resolved. Advised owner to replace brake fluid every 2 years or 40,000 km.
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.