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 8

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 8 indicates a medium-severity fault in the IPB braking ECU’s right rear wheel inlet valve drive circuit. This may be caused by an open or short circuit in the inlet valve solenoid coil, or a failed internal ECU driver component. ABS, ESP, and AEB may be disabled, though basic braking remains. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Open or short circuit in right rear inlet valve solenoid coil inside IPB electro-hydraulic module (resistance value outside 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.
  • 4Overdue brake fluid replacement causes contamination and deterioration, mechanically binding the inlet valve spool. The resulting abnormal drive current triggers fault protection.
  • 5Unstable IPB module power supply voltage or poor ground connection causes the ECU to misinterpret 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 for corroded, bent, or backed-out connector pins. Measure the wiring harness continuity from the connector to the ECU.
  • 3
    Disconnect the IPB connector and 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 resistance with the left rear wheel (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' (Actuator Test). Listen for the right rear inlet valve actuation sound. If other valves click but the right rear valve produces no sound, or 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, the Song PLUS DM-i typically uses an assembly including the 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). Follow the sequence: right rear - left rear - right front - left front. Verify no air locks remain in the lines.
  • 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 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 Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.