AU
C001900

DTC C001900 indicates a malfunction in the drive circuit or mechanical components of the Rear Left Outlet Valve inside the IPB (Integrated Power Brake) hydraulic control unit — Atto 3

Braking System

DTC C001900 indicates a malfunction in the drive circuit or mechanical components of the Rear Left Outlet Valve inside the IPB (Integrated Power Brake) hydraulic control unit.

During ABS/ESC operation, this solenoid valve controls brake fluid return from the left rear wheel cylinder to the low-pressure accumulator or reservoir to precisely regulate wheel cylinder pressure.

The ECU detects an abnormal valve drive current (open circuit, short circuit, or short to ground/power) or mechanical sticking of the valve spool, preventing the IPB from releasing pressure at the left rear wheel.

This fault triggers ESP system degraded mode and may limit ABS, ESC, energy recovery, and automatic emergency braking functions.

The system usually retains conventional hydraulic braking (depending on the IPB failsafe strategy).

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Open circuit, short circuit, or short to ground in the left rear outlet valve solenoid coil inside the IPB hydraulic unit, causing the drive current to exceed the calibrated threshold (typical abnormal range: 0.3-1.5A).
  • 2Brake fluid contamination (excessive water content, metal debris, or gel-like sediment) causes the outlet valve spool to stick in the open or closed position, and the ECU detects abnormal position feedback.
  • 3IPB ECU internal valve body drive circuit fault, such as a damaged power MOSFET, burnt sampling resistor, or poor solder joint on the driver chip.
  • 4Water ingress, oxidation, or terminal back-out at the IPB wiring harness connector (32-pin or 48-pin main connector), causing excessive contact resistance in the valve body drive circuit.
  • 5Abnormal return fluid pressure surge from the left rear brake caliper or line causing mechanical damage to the valve body (common in vehicles with long-overdue brake fluid replacement)
What To Do
  • 1
    Use the BYD VDS2000 or a diagnostic tool to access the IPB system. Read and confirm C001900 is a current fault (Active). Record the vehicle speed, hydraulic pressure, and valve body drive current values from the freeze frame data (Freeze Data).
  • 2
    Clear the fault code and perform the IPB dynamic function test: in a safe area, brake sharply at 20-40 km/h to trigger ABS operation and observe if the fault recurs. If it recurs, confirm a hardware fault.
  • 3
    Disconnect the IPB assembly wiring harness connector. Inspect the terminals for corrosion or water ingress (focus on the pin seals). Measure the left rear outlet valve solenoid resistance (standard value is typically 2-6 Ω, depending on the specific model). If the resistance is infinite or near 0 Ω, this confirms valve body damage.
  • 4
    Check that the voltage of the IPB power supply circuits (terminal 30 constant power, terminal 15 ignition power) is 12V ± 0.5V, the ground wire resistance is less than 1Ω, and the CAN-H and CAN-L line voltages are normal (approximately 2.5V).
  • 5
    If circuit measurements are normal but resistance is abnormal, or if the fault returns quickly after clearing, replace the IPB integrated brake assembly (part number varies by model; e.g., Song PLUS DM-i uses the 6A-3555100 series). Do not replace the hydraulic valve body separately.
  • 6
    After replacement, perform the complete repair procedure: bleed brake lines (use dedicated brake bleeding equipment or traditional two-person bleeding method) → calibrate steering angle sensor (G85) → calibrate longitudinal acceleration sensor → calibrate yaw rate sensor → perform road test to verify ABS/ESP function
Real-World Cases
BYD DTC AI Analysis

BYD Seal 06 DM-i left rear outlet valve drive fault

✓
Vehicle: 2024 Seal 06 DM-i 120KM flagship variant, 8,500km. Symptoms: Dashboard intermittently displayed "Check ESP System", ABS and ESC warning lights illuminated, brake pedal felt normal. Diagnosis: Connected VDS2000 and scanned the IPB system. Retrieved current DTC C001900 (Left Rear Outlet Valve Drive Fault). Freeze frame showed vehicle speed was 35km/h when the fault occurred, with left rear outlet valve drive current at 0A (open circuit characteristic). Measured infinite resistance between Pin23 (Left Rear Outlet Valve +) and Pin24 (Left Rear Outlet Valve -) at IPB harness connector C07. Confirmed the hydraulic unit's internal solenoid coil had an open circuit. Repair: Replaced the IPB integrated brake assembly (Part No.: 6A-3555100-00). Performed brake bleeding and sensor calibration. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song PLUS DM-i Hydraulic Unit Valve Body Sticking

✓
Vehicle: 2021 Song PLUS DM-i 110KM Flagship PLUS, 42,000km. Symptoms: ESP warning light suddenly lit up during high-speed driving with "Check Brake System" alert; regenerative braking failed. Diagnosis: Scan tool pulled stored code C001900 from the IPB system plus C001800 (left rear inlet valve fault). Found complete failure of the left rear hydraulic valve assembly. Opened the IPB reservoir to find brake fluid dark brown (should be pale yellow) contaminated with metal debris. Root cause: Brake fluid never changed (over 40,000km), causing the valve spool to seize from lack of lubrication; high current draw burned out the ECU driver circuit. Repair: Replaced the IPB assembly, thoroughly flushed the brake lines, replaced all brake fluid with DOT4. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro DM IPB hydraulic control unit fault

✓
Vehicle: 2019 BYD Qin Pro DM Super, 67,000 km. Symptoms: "Braking System Fault" warning on cold starts. Light cleared after driving but fault recurred. Diagnosis: DTCs C055F00 (Hydraulic Unit Abnormal) and intermittent C001900 stored. Found green corrosion inside 32-pin IPB harness connector (vehicle had been driven through water), causing intermittent open circuit in left rear outlet valve drive line. Cleaning the connector did not resolve. Valve body coil resistance measured 3.2Ω cold but drifted above 8Ω hot, confirming internal coil insulation degradation. Repair: Replaced IPB integrated braking unit and sealed wiring harness. Fault resolved.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.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.
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.