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C007500

DTC C007500 indicates an electrical fault or short circuit in Master Cylinder Position Sensor A within the IPB (Intelligent Power Brake) system — Seal U

Braking System

DTC C007500 indicates an electrical fault or short circuit in Master Cylinder Position Sensor A within the IPB (Intelligent Power Brake) system.

This sensor typically uses a Hall-effect or inductive principle and mounts near the brake master cylinder.

It monitors master cylinder piston travel in real time, converting the driver's mechanical braking intent into an electrical signal (typically a 0.5-4.5V analog voltage) and transmitting it to the IPB ECU.

The ECU uses this signal to calculate the required brake fluid pressure and controls the motor to build hydraulic pressure.

The ECU sets this DTC when it detects the sensor signal voltage continuously exceeding the valid range (short to power >4.8V or short to ground <0.2V), or an abnormal logical relationship between the signal and pedal travel.

Setting this DTC causes the IPB system to enter a degraded mode, disable brake energy recovery, retain only basic hydraulic braking, and illuminate the ABS/ESC warning light.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Sensor harness wear or crushing causing short to power or ground: The IPB assembly is located near the engine compartment firewall. Vibration may rub the harness against sharp body edges, or front compartment repairs may crush the harness, damaging the insulation.
  • 2Connector water ingress or oxidation corrosion: A poor seal on the sensor plug (usually located in the middle of the IPB assembly) allows water entry during car washing, wading, or damp conditions. This causes pin oxidation or electrolytic corrosion, resulting in abnormal resistance or a short circuit.
  • 3Master cylinder position sensor internal fault: Aging of the internal Hall element, cold solder joints, or a coil short circuit causes an abnormal output signal. This fault typically occurs in high-temperature environments or high-mileage vehicles (>80,000 km).
  • 4IPB control module internal signal processing circuit fault: A damaged ECU internal ADC sampling circuit or signal conditioning chip misjudges a normal sensor signal as a fault or fails to supply a stable 5 V reference voltage to the sensor.
  • 5Mechanical offset of the sensor mounting position: Misalignment between the sensor and master cylinder piston after IPB assembly removal and installation causes the air gap to exceed the design range. The system identifies the abnormal signal amplitude as a short circuit.
What To Do
  • 1
    Freeze frame analysis: Use a dedicated BYD diagnostic tool (VDS or EDS) to read the fault code freeze frame data. Record the vehicle speed, brake pedal status, battery SOC, and IPB motor status at the time of the fault. Determine whether the fault is intermittent during driving or continuous while stationary.
  • 2
    Visual and wiring harness inspection: Raise the vehicle and inspect the IPB assembly (located at the firewall above the brake pedal) for impact deformation or water marks. Follow the sensor wiring harness (usually routed from the top of the IPB) and check for wear, damaged insulation, or interference points with the vehicle body. Carefully inspect the rubber grommet at the firewall pass-through.
  • 3
    Connector inspection: Disconnect the sensor connector on the IPB assembly (usually featuring a waterproof locking tab) and check the pins for green oxidation, backed-out terminals, or enlarged terminal holes. Measure the voltage to ground at the connector power supply terminal (usually Pin1 or Pin3; refer to the vehicle wiring diagram) and confirm it is 5V±0.25V. If the voltage is abnormal, check the IPB ECU power supply.
  • 4
    Signal circuit measurement: Use an oscilloscope or multimeter to measure the sensor signal wire voltage. While pressing the brake pedal, the voltage should change smoothly (0.5V-4.5V). If jumps, spikes, or a fixed high/low voltage occur, disconnect the sensor connector and measure the insulation resistance from the wiring harness side to ground and to power. Resistance should be >10MΩ.
  • 5
    Sensor body test: If the wiring is normal, remove the master cylinder position sensor (some models require replacing the IPB as a complete unit). Move a magnet close to the sensor's sensing face and measure whether the output voltage changes with magnetic field strength. If the voltage remains fixed, the sensor has internal damage.
  • 6
    IPB assembly replacement and calibration: If the sensor cannot be replaced separately or an internal ECU fault exists, replace the IPB intelligent power brake assembly. After replacement, use the diagnostic tool to perform the 'IPB Bleeding' and 'Pedal Position Sensor Calibration' procedures; otherwise, the fault warning lamp remains illuminated and brake pedal travel is abnormal.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i master cylinder sensor short circuit after water fording

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The vehicle drove through approximately 40 cm of water. The dashboard displayed "Brake System Fault." Retrieved DTC C007500. Inspection found visible water stains on the lower IPB assembly and water accumulation inside the sensor connector. Disassembling the connector revealed a water film bridging pin 3 (signal line) and pin 2 (ground line), causing a signal short to ground. Cleaned the connector pins with anhydrous ethanol, blow-dried them, applied conductive grease, and cleared the fault. Check the sealing around the IPB mounting location and install a waterproof cover if necessary.
BYD DTC AI Analysis

Han EV wiring harness wear causes intermittent C007500 fault

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Owner reported intermittent ABS warning light. Scanner retrieved historic DTC C007500, current status intermittent. Found IPB sensor wiring harness contacting metal bracket edge near steering column mount; insulation worn through exposing copper wire. Harness movement during steering caused intermittent short to ground at the damaged section. Wrapped damaged section with insulation tape, re-secured harness routing, added rubber grommet to isolate from sharp metal edge. Cleared DTC and road tested 100 km with no recurrence.
BYD DTC AI Analysis

BYD Seal IPB Assembly Internal Sensor Failure Replacement Case

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At 12,000 km, the dashboard displayed "Check Brake System". DTC C007500 present and would not clear. Sensor supply measured 5V (normal). Signal voltage fixed at 4.9V, not varying with pedal movement (normal: 0.5–4.5V). Wiring insulation good. Found internal master cylinder position sensor failure in the IPB (Hall IC failure). Sensor integrates with IPB housing; replaced complete IPB assembly (Part No.: 3510001-XX). Completed IPB bleed and pedal position calibration after replacement. Fault cleared.
BYD DTC AI Analysis

Sensor mounting position shifted after accident repair on Qin PLUS DM-i

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After front collision repairs (front bulkhead replacement), the ABS warning light illuminated on the instrument cluster with DTC C007500. Inspection revealed the IPB assembly had been removed during the accident repairs. Upon reinstallation, the locating pins were not aligned, causing excessive clearance between the master cylinder position sensor and the master cylinder piston magnetic ring (standard clearance 0.5-1.2mm, measured 2.8mm). The sensor could not detect changes in magnetic field strength, so the ECU set a signal open/short circuit fault. Removed and reinstalled the IPB, ensuring the locating pins were fully seated. Tightened the mounting nuts to the specified torque (typically 8-10Nm). The DTC cleared automatically and brake pedal feel returned to normal.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.