AU
C001D04

This DTC indicates an electrical or mechanical fault in the right rear wheel outlet valve (discharge valve/release valve) inside the ABS (Anti-lock Braking System) hydraulic modulator assembly — Qin Plus

Braking System

This DTC indicates an electrical or mechanical fault in the right rear wheel outlet valve (discharge valve/release valve) inside the ABS (Anti-lock Braking System) hydraulic modulator assembly.

This solenoid valve is a key actuator in the ABS hydraulic unit and controls the release of hydraulic pressure from the right rear wheel brake caliper during the ABS activation cycle.

The ECU sets this DTC when it detects an open circuit, short circuit, short to ground, or short to power in the solenoid valve circuit, or when the valve spool fails to open or close normally due to mechanical sticking.

This fault causes the right rear wheel ABS pressure regulation function to fail.

During emergency braking, the right rear wheel may fail to release pressure normally (causing premature lock-up) or retain pressure abnormally, severely affecting braking stability and safety.

The system enters fail-safe mode, disables the ABS, EBD, and ESC functions, and illuminates the relevant warning lamps.

The C001D04 fault code on the Qin Plus indicates an electrical or mechanical fault in the right rear ABS outlet valve inside the hydraulic modulator. Severity is medium because ABS, EBD, and ESC may be disabled, reducing braking stability in emergency stops. Common causes include a faulty solenoid coil or a damaged ABS ECU valve driver circuit. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Open circuit, short circuit, or resistance drift in the right rear wheel outlet valve solenoid coil inside the ABS hydraulic modulator assembly.
  • 2Damaged ABS ECU internal solenoid valve drive circuit (e.g., burnt driver chip or power MOSFET, or cold solder joint)
  • 3Brake fluid contamination, deterioration, or impurities cause solenoid valve spool sticking, sealing ring swelling, or hydraulic circuit blockage.
  • 4Water ingress, oxidation, corrosion, or pin back-out at the wiring harness connector causes poor contact in the solenoid valve control circuit.
  • 5Abnormal system power supply voltage (below 9V or above 16V) or poor grounding causes insufficient solenoid valve drive current.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS or ED400) to read the complete fault codes. Confirm C001D04 is a current fault and does not clear. Record the freeze frame data.
  • 2
    Check the ABS system power supply: Measure the voltage at the ABS ECU power pin. The voltage must be within 9-16V (normally about 12.5V). Check the fuse, relay, and power wiring.
  • 3
    Check the ground system: Measure the resistance between the ABS ECU ground harness and the body ground. The resistance must be less than 1Ω. Check the ground point for looseness or oxidation.
  • 4
    Disconnect the ABS ECU connector and visually inspect the right rear wheel outlet valve control pin (refer to the wiring diagram for the specific pin number) for water ingress, corrosion, or burn marks.
  • 5
    Perform the solenoid valve active test (actuation test): Trigger the right rear wheel outlet valve using the diagnostic tool and listen for a crisp clicking sound. No sound indicates a mechanical or electrical fault in the internal solenoid valve.
  • 6
    Check the brake fluid level, quality, and color. If necessary, extract brake fluid to inspect for metal debris or gel contaminants.
  • 7
    If confirming the fault is inside the hydraulic modulator, replace the ABS hydraulic modulator assembly (with ECU, as BYD models usually do not support separate solenoid valve replacement).
  • 8
    After installing the new assembly, bleed the brake lines according to the standard procedure (using dedicated bleeding equipment or manual bleeding). Use a diagnostic tool to perform system calibration, wheel speed sensor signal checks, and road test verification.
Real-World Cases
BYD DTC AI Analysis

BYD Qin ABS solenoid valve internal open circuit fault

✓
ABS and ESP warning lights remained on. Owner reported abnormal brake feel at the right rear wheel. Scan tool retrieved fault code C001D04 (right rear outlet valve fault). Battery voltage measured 12.4V – normal. ABS ECU ground connection secure. Vehicle sat for 10 minutes; rescanned – fault code still present. Performed solenoid activation test – no actuation sound from right rear outlet valve. Measured internal solenoid resistance: open circuit. Diagnosed as internal ABS ECU solenoid failure. Replaced ABS hydraulic modulator assembly and performed bleeding calibration. Fault completely resolved.
Original source ↗
BYD DTC AI Analysis

BYD e5 Pure Electric Vehicle ABS Hydraulic Unit Failure

✓
The dashboard displayed "Check ABS System" and the ABS warning light stayed on. The right rear wheel locked up during emergency braking tests. Scanned with a diagnostic tool and retrieved DTC C001D04. Checked HV system insulation — normal. Ruled out HV interference. Measured 12V supply — normal. Swapped left and right rear wheel speed sensors; DTC still pointed to right rear outlet valve. Confirmed internal solenoid valve fault in ABS hydraulic control unit. Replaced ABS assembly and completed system configuration. ABS function returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Song ABS Pump Solenoid Valve Sticking

✓
ABS warning light suddenly illuminated while driving. When vehicle speed exceeded 40 km/h, slight chassis vibration developed. Connected a scan tool and retrieved DTC C001D04 (right rear outlet valve fault). Inspected right rear wheel speed sensor and wiring connections; normal. Brake fluid level normal. Performed solenoid valve actuation test via scan tool: right rear outlet valve showed no response, other wheel solenoids operated normally. Measured solenoid resistance: infinite (open circuit). Determined internal ABS pump assembly solenoid had failed. Replaced ABS pump assembly; fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD F3 ABS ECU internal drive circuit fault

✓
After starting the vehicle, the ABS warning light stayed on, with intermittent beeping while driving. Connected an OBD scanner and retrieved fault code C001D04. Inspected the ABS fuse and relay; both functioned correctly. Checked the right rear wheel cylinder and hydraulic lines and found no leaks. Verified the vehicle had no history of overheating, ruling out false triggers from thermal protection. Used an oscilloscope to check the solenoid valve drive signals; the ECU was not outputting a drive waveform. Isolated the fault to an internal drive circuit failure in the ABS ECU. Replaced the ABS electronic control unit assembly, cleared the fault code, and restored system functionality.
Original source ↗
BYD DTC AI Analysis

Abnormal ABS power supply caused solenoid valve failure in BYD models

✓
ABS warning light on with DTCs C001D04 and C0121 (solenoid valve relay fault) stored. With the vehicle stationary, heard abnormal solenoid valve relay chattering. Measured ABS solenoid valve supply voltage at only 9.5V (low). Checked ABS fuse holder: poor contact with slight burn marks. Cleaned fuse holder and tightened ground; voltage returned to normal, C0121 cleared, but C001D04 remained. Further testing confirmed right rear outlet valve failure. Replaced ABS assembly. 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.