AU
C05C200

DTC C05C200 indicates the electric booster motor operating temperature in the IPB (Intelligent Power Brake) integrated brake system exceeds the safety threshold (typically 120°C–130°C) — Qin Plus

Braking System

DTC C05C200 indicates the electric booster motor operating temperature in the IPB (Intelligent Power Brake) integrated brake system exceeds the safety threshold (typically 120°C–130°C).

The IPB system uses a brushless DC motor to drive the brake master cylinder and generate hydraulic boost, completely replacing the traditional vacuum booster.

When the motor temperature sensor (NTC thermistor) detects an abnormal temperature rise in the motor windings or drive module, the ECU stores this DTC and initiates a protection strategy.

This strategy limits motor power output, illuminates the ABS/ESC warning light, and may switch the system to a degraded mode (no boost or hydraulic brake backup).

This fault results in a noticeably harder brake pedal, increases required pedal force, and extends braking distance, posing a severe safety hazard during continuous braking or high-speed driving.

The C05C200 fault code on the Qin Plus indicates the IPB electric brake booster motor is overheating beyond its safety limit. Severity is medium because braking assist may be reduced, making the pedal harder and increasing stopping distance. Common causes include brake drag from sticking calipers or poor brake cooling/blocked airflow around the IPB module. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Brake drag or poor return: Brake caliper piston corrosion, binding guide pins, or improper brake pad installation causes continuous clamping. The motor must operate continuously to maintain pressure, generating excessive heat.
  • 2Cooling system fault: Mud or sand blocking the cooling air duct at the IPB module installation position, poor heat dissipation inside the compartment, or continuously high ambient temperatures (such as during prolonged aggressive driving or towing mode).
  • 3Abnormal mechanical load: deteriorated or water-contaminated brake fluid causing increased master cylinder piston resistance, partial brake line blockage, or motor bearing wear causing reduced transmission efficiency.
  • 4Control strategy defect: Outdated IPB ECU software, abnormal motor PWM control duty cycle, or incorrect stall protection threshold settings cause prolonged full-load motor operation.
  • 5Motor assembly fault: Motor winding insulation aging (insulation resistance <1MΩ), abnormal Hall sensor signal, or drive MOSFET overheating reduces energy conversion efficiency and generates Joule heat.
What To Do
  • 1
    Freeze frame analysis: Use VDS2000 or a dedicated diagnostic tool to read freeze frame data from when the fault occurred, including ambient temperature, motor temperature, brake pressure, and motor current. Verify actual overheating rather than a false sensor reading.
  • 2
    Visual and cooling inspection: Inspect the IPB module exterior for impact damage. Clean dust and oil from the heat sink surface. Verify the mounting bracket has no deformation causing poor contact with the cooling surface.
  • 3
    Brake system drag detection: Raise the vehicle, shift to N, and manually rotate all four wheels to check for binding. Press and release the brake pedal, observe if the brake pads return promptly, and measure the residual brake drag.
  • 4
    Electrical verification: Disconnect the IPB wiring harness, measure the motor temperature sensor resistance (approximately 10 kΩ at 25°C), and compare it with the temperature-resistance curve. Measure the motor three-phase winding resistance balance (deviation <5%) and insulation resistance to ground (must be >20 MΩ).
  • 5
    Hydraulic system check: Extract brake fluid and inspect for black discoloration or impurities. Verify the brake master cylinder piston slides smoothly. If necessary, replace the brake fluid and bleed the system (use dedicated bleeding equipment).
  • 6
    Software update and calibration: Check the IPB ECU software version and update to the latest version (such as the post-2023 release with optimized thermal management strategy). Perform brake pressure sensor calibration and motor zero-position learning.
  • 7
    Assembly replacement: If motor insulation resistance is <1MΩ, drive current remains >18A (normal idle <5A), or the fault code frequently triggers despite normal heat dissipation, replace the IPB electro-hydraulic module assembly with ECU, and complete coding and system bleeding.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i IPB overheat protection activates during prolonged downhill braking

✓
After 15 km of continuous downhill, the ABS and ESC warning lights lit up and the brake pedal stiffened. Scanner read DTC C05C200; freeze frame showed motor temperature at 138°C. Inspection found no brake drag and the heat sink normal. Continuous braking kept the motor running constantly, causing heat buildup. Fix: Updated IPB software to latest version (optimized thermal management for long downhills, added intermittent motor operation). Advised driver to use regenerative braking (high recuperation mode) together with braking, avoiding continuous heavy pedal application. Fault has not recurred.
BYD DTC AI Analysis

Contaminated brake fluid caused master cylinder sticking, leading to motor overheating

✓
Came in for routine service with the IPB warning light on. Scanned DTC C05C200. Found brake fluid severely blackened (water content >4%) and master cylinder piston sliding resistance significantly increased. Disassembled the IPB; internal piston seals were swollen and deformed. The contaminated, high-viscosity fluid forced the motor to draw excessive current—22A measured against a normal 10A—to drive the master cylinder, causing rapid temperature rise. Replaced the IPB assembly (internal piston worn), flushed the brake lines thoroughly, refilled with DOT4 low-viscosity brake fluid, and bled the system. Advised customer to replace brake fluid every 2 years.
BYD DTC AI Analysis

Blocked IPB heat sink caused false motor overheat warning

✓
During hot summer weather, the owner reported the warning light illuminated after one hour of congested urban driving, clearing after the vehicle cooled. Inspection found the IPB mounted beneath the battery with cooling fins completely blocked by lint and dust, severely reducing heat exchange. Infrared thermometer measured motor housing temperature at 125°C (normal: <80°C). Resolution: Thoroughly cleaned the cooling fin air ducts, installed a heat insulation pad beneath the IPB to prevent battery heat radiation, and advised the owner to check the engine bay regularly for cleanliness. Tracked for one month after cleaning—fault has not returned.
BYD DTC AI Analysis

False alarm caused by temperature sensor drift

✓
The vehicle set a C05C200 fault code immediately on cold start. Ambient temperature was only 15°C — the motor could not possibly be overheating. Measured the temperature sensor resistance and found only 3kΩ at room temperature (corresponding to approximately 60°C), seriously deviating from the standard curve (10kΩ@25°C). Sensor drift caused the ECU to falsely detect motor overheat. Further inspection revealed oxidised and corroded pins on the IPB wiring harness (the vehicle had previously been driven through water). Solution: Cleaned the wiring harness pins, applied conductive paste, and replaced the temperature sensor. Since the sensor is integrated inside the IPB, this required replacing either the entire motor assembly or the IPB assembly. After replacement the fault code cleared and the data stream showed normal temperature.
BYD DTC AI Analysis

Frequent ESC intervention overloaded the power steering motor

✓
Customer reported the warning light came on after driving on icy winter roads. Diagnosis revealed DTC C05C200 accompanied by C005108 (steering angle sensor fault). Steering angle signal drift caused the ESC to falsely detect instability, triggering continuous active braking (frequent hydraulic pump cycling) and overheating the assist motor. Inspection found the steering angle sensor mounting position was offset. Fix: Recalibrated the steering angle sensor (neutral position adjustment), updated ESC control logic (software upgrade), and performed a cooling reset on the IPB. Advised the customer to stop and rest the vehicle if warnings appear after extreme road conditions.
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.