NO
AU
C001504

DTC C001504 indicates a circuit or functional fault in the Right Front Outlet Valve inside the Anti-lock Braking System (ABS) Hydraulic Control Unit (HCU) assembly — Atto 8

Braking System

DTC C001504 indicates a circuit or functional fault in the Right Front Outlet Valve inside the Anti-lock Braking System (ABS) Hydraulic Control Unit (HCU) assembly.

This solenoid valve is a core component of the ABS actuator.

It opens during the pressure reduction phase of the anti-lock control cycle to release hydraulic pressure from the right front wheel brake cylinder.

The ABS ECU sets this fault code when it detects an open or short circuit in the valve drive circuit, or an abnormal valve spool response (such as sticking or a response timeout).

This fault disables the ABS pressure regulation function for the right front wheel.

During emergency braking, the wheel may lose anti-lock protection and lock up prematurely, severely compromising braking performance and driving safety.

This condition may also trigger a degraded operating mode in related systems, including Electronic Stability Control (ESC) and Automatic Emergency Braking.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD E5 front right outlet valve coil open circuit fault

✓
While driving, the ABS and ESC warning lights suddenly came on. Brake pedal feel remained normal. Connected VDS2000 and retrieved DTC C001504. During actuator testing, the right front outlet valve produced no actuation sound; the other three valves operated normally. Disconnected the ABS pump harness connector and measured infinite resistance (open circuit) across the right front outlet valve pins. Diagnosis: burnt solenoid coil inside the HCU. The ABS pump assembly was under warranty, so replaced the genuine ABS hydraulic modulator assembly (with ECU). Performed the bleed procedure and online matching. Fault cleared. Road-tested 20 km with no abnormalities.
Original source ↗
BYD DTC AI Analysis

Chafed BYD E5 ABS pump wiring harness caused intermittent short circuit

✓
The owner reported the ABS warning light tends to come on during rain or after driving through water, sometimes going out automatically in dry weather. The diagnostic scanner logged an intermittent C001504 fault. Inspection revealed the ABS hydraulic modulator assembly wiring harness had chafed at the firewall retaining clip; damaged insulation caused an intermittent short to body on the right front outlet valve drive wire. Technicians repaired the harness (re-soldered the connections and fitted corrugated tubing), adjusted the routing to prevent body interference, and sealed against water ingress. They cleared the fault codes and conducted a simulated rain test; the fault did not return.
Original source ↗
BYD DTC AI Analysis

BYD E5: Brake fluid contamination caused outlet valve sticking

✓
Vehicle entered limp mode with the instrument cluster displaying "Check Brake System" and ABS/ESP warning lights on steady. Diagnosis revealed DTC C001504. Solenoid resistance measured normal at 2.8Ω. Actuator test showed sluggish valve spool movement with occasional faint noise. Owner confirmed brake fluid never changed in 60,000 km. Severe moisture absorption caused the fluid to deteriorate and crystallize, jamming the valve spool. Replaced ABS hydraulic modulator assembly, thoroughly flushed brake system (replacing hoses and wheel cylinders), and refilled with fresh DOT4 brake fluid. Fault cleared.
Original source ↗
BYD DTC AI Analysis

Right front brake line resonance caused valve body weld cracking on BYD E5

✓
ABS warning light illuminates intermittently, more frequently on rough roads. DTC C001504. Found the right front brake hard pipe mounting bracket loose with excessive pipe slack; the line resonated against the body while driving. Long-term vibration transmitted to the ABS pump body caused micro-cracks in the PCB solder joints at the internal right front outlet valve, creating intermittent open circuits. Re-secured the bracket, added vibration dampers to the line, and replaced the ABS hydraulic modulator assembly. Fault eliminated completely.
Original source ↗
BYD DTC AI Analysis

Internal hydraulic modulator defect in new BYD E5

✓
At 8,000 km, the dashboard suddenly displayed "Check Brake System." The ABS, ESC, and automatic emergency braking warning lights illuminated simultaneously; auto hold failed. The dealership diagnosed fault code C001504. Resistance measurement of the right front outlet valve showed 12 Ω (far above the 2–5 Ω specification), indicating an internal inter-turn short in the solenoid coil (partial short). Replaced the OEM ABS hydraulic modulator assembly (part number 3635010-xx). Cleared the fault codes, performed ABS dynamic testing and a 50 km road test. All systems returned to normal.
Original source ↗
Other Atto 8 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.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.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.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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.