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 — Qin Plus

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 Qin Plus 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 from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 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.
  • 3Loose IPB wiring harness connector (usually located on the top or side of the module), corrosion from water ingress, or oxidized pins causing excessive contact resistance.
  • 4Contaminated and degraded brake fluid from overdue replacement mechanically binds the inlet valve spool, causing abnormal drive current and triggering 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 all fault codes 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 for leaks. Disconnect the battery negative terminal, then check the connector pins for corrosion, bending, or backing out. Measure the continuity of the wiring harness 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). Standard value: 3-7 Ω. Compare this value with the left rear wheel resistance (C001800 circuit). A deviation exceeding 2 Ω indicates a faulty valve body.
  • 4
    Connect the diagnostic tool and perform the 'Hydraulic Unit Actuator Test' (Actuator Test). Listen for the right rear inlet valve actuation 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 vehicle model; for example, Song PLUS DM-i typically uses an assembly with an ECU). Never dismantle 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 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: apply emergency braking at speeds exceeding 40 km/h to test ABS operation; check the ESP OFF switch function; and verify 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 Qin Plus 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.