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 — Qin Plus

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).

The C001900 fault code on the Qin Plus indicates a medium-severity problem with the rear left outlet valve in the IPB hydraulic brake unit. This valve helps control brake pressure during ABS or ESC operation. Common causes include an open or short circuit in the valve solenoid, or a stuck valve caused by contaminated brake fluid. 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 circuit, short circuit, or short to ground in the left rear outlet valve solenoid coil inside the IPB hydraulic unit causes the drive current to exceed the calibrated threshold (abnormal range typically 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; the ECU detects abnormal position feedback.
  • 3IPB ECU internal valve body drive circuit fault, such as a damaged MOSFET power transistor, burnt sampling resistor, or cold 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 shock from the left rear brake caliper or lines causes mechanical damage to the valve body (common in vehicles with long-overdue brake fluid replacement).
What To Do
  • 1
    Use BYD VDS2000 or a diagnostic tool to access the IPB system, read and confirm C001900 is a current fault (Active), and 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 the ABS. Observe if the fault recurs; if it recurs, confirm a hardware fault.
  • 3
    Disconnect the IPB assembly wiring harness connector. Check the terminals for corrosion or water ingress (focus on the pin seals). Measure the left rear outlet valve solenoid resistance (standard value is usually 2-6 Ω, depending on the specific model). If the resistance is infinite or close to 0 Ω, this confirms valve body damage.
  • 4
    Check that the voltage of the IPB power supply circuits (constant power terminal 30 and ignition switch terminal 15) is 12V±0.5V, the ground wire resistance is less than 1Ω, and the CAN-H and CAN-L wire voltages are normal (approximately 2.5V).
  • 5
    If wiring measurements are normal but resistance is abnormal, or the fault recurs quickly after clearing, replace the IPB integrated brake assembly (part numbers vary 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 method) → calibrate steering angle sensor (G85) → calibrate longitudinal acceleration sensor → calibrate yaw rate sensor → 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

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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

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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

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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 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.