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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) — Atto 3

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.

5
Cases Logged
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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.