NO
AU
C001000

This DTC indicates the IPB (Intelligent Integrated Braking System / One-Box Integrated Braking System) ECU detected an electrical fault in the left front inlet valve (normally open valve) drive circuit — Seal U

Braking System

This DTC indicates the IPB (Intelligent Integrated Braking System / One-Box Integrated Braking System) ECU detected an electrical fault in the left front inlet valve (normally open valve) drive circuit.

The inlet valve is a key solenoid valve in the ABS/ESC hydraulic modulator.

It controls the brake fluid path from the brake master cylinder to the left front wheel brake cylinder.

A "drive fault" occurs when the ECU detects an abnormal circuit condition while supplying power to the solenoid valve coil (typical resistance 3-6Ω) through the driver chip (usually an H-bridge driver or high-side drive MOSFET).

These abnormal conditions include an open coil circuit, short to power, short to ground, driver chip over-temperature protection, or an abnormal drive circuit power supply.

This fault prevents the left front wheel from establishing normal ABS/ESC pressure regulation and triggers system degradation (ABS/ESC function limited or disabled).

The system retains only basic hydraulic braking, severely compromising vehicle active safety performance.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i: IPB water ingress after wading caused left front inlet valve driver fault

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After wading through water, the dashboard displayed 'Check ABS System'. The scan tool retrieved DTC C001000 (active fault). Inspection found the IPB mounted low; splashing during the wade compromised the IPB wiring harness connector seal and allowed water ingress. Opening the connector revealed green oxidised pins. Cleaned the connector with electronic cleaner, dried it, reapplied conductive grease, and ensured the sealing ring seated properly. Cleared the DTC and monitored for one week; the fault did not recur.
BYD DTC AI Analysis

Replaced IPB assembly due to open circuit in internal solenoid coil.

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2021 Song PLUS DMi at 30,000 km, ABS warning light illuminated while driving. Diagnosis showed C001000 static fault. Removed IPB assembly, disconnected electro-hydraulic module from ECU, and measured left front inlet valve coil pin directly. Resistance read infinite (normal: 4.5Ω), indicating open circuit in valve body internal coil. As IPB is highly integrated, replaced IPB electro-hydraulic module assembly. Performed bleed procedure and ESC calibration; fault resolved.
BYD DTC AI Analysis

Contaminated brake fluid caused the valve to stick, triggering a false warning.

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Vehicle set C001000 one week after an unauthorised shop replaced the brake fluid with inferior product. Inspection found the fluid cloudy and milky white (severely water-contaminated). The inferior fluid corroded and seized the inlet valve spool; the ECU detected abnormal drive current (excessive draw or response timeout) and logged the fault. Replaced the IPB electro-hydraulic module (internally contaminated), thoroughly flushed all brake lines, replaced all brake hoses and wheel cylinders, then refilled with DOT4 fluid and bled the system.
BYD DTC AI Analysis

Intermittent fault caused by software calibration error

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Intermittent C001000 fault code found during new vehicle delivery PDI. No abnormal braking feel. Checked wiring harness and valve body resistance – both normal. Consulted technical bulletin: this batch of IPB software has overly strict solenoid drive diagnostic thresholds. Upgraded IPB ECU software to latest version (V2.1 or above). Fault code no longer appears after upgrade; no hardware replacement required.
BYD DTC AI Analysis

False fault caused by poor IPB ground

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After accident repairs, the vehicle set DTC C001000 and multiple IPB-related fault codes. Inspection found the IPB ground bolt loose from the collision repair, causing high ground resistance (measured 2.3Ω; spec <0.1Ω). The poor ground dropped solenoid drive voltage, causing the ECU to flag a false drive-circuit fault. Sanded the ground terminal, tightened the bolt to spec (8–10Nm), and cleared the fault.
Other Seal U 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.