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 — Atto 3

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 Atto 3 indicates a medium-severity fault in the right rear wheel inlet valve drive circuit within the IPB braking system. It may be caused by an open or shorted inlet valve solenoid coil, or a failed ECU valve driver component. 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.
3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Open or short circuit in the right rear inlet valve solenoid coil inside the IPB electro-hydraulic module (resistance outside the standard 3-7 Ω 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 pin oxidation causing excessive contact resistance.
  • 4Overdue brake fluid replacement leads to contamination and deterioration, mechanically binding the inlet valve spool. The resulting abnormal drive current triggers fault protection.
  • 5Unstable IPB module power supply voltage or a 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 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 exterior for leaks. Disconnect the battery negative terminal, then check if the connector pins are corroded, bent, or backed 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 corresponding to 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 operating sound. If the 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
    If diagnostics confirm an internal IPB fault, replace the entire IPB electro-hydraulic module assembly (BYD part numbers vary by model; for example, the Song PLUS DM-i typically uses an assembly with an 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: apply emergency braking at speeds exceeding 40 km/h to test ABS operation, check the ESP OFF switch function, and confirm no fault 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 Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.