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C05D000

This DTC indicates the signal difference between dual redundant channels A and B of the Master Cylinder Position Sensor inside the IPB (Intelligent Integrated Braking System) exceeds the diagnostic threshold — Atto 3

Braking System

This DTC indicates the signal difference between dual redundant channels A and B of the Master Cylinder Position Sensor inside the IPB (Intelligent Integrated Braking System) exceeds the diagnostic threshold.

For functional safety (ISO 26262), the IPB uses a dual-channel redundant design to monitor brake master cylinder piston travel.

When the difference between the two signals continuously exceeds the calibrated value (typically 5%-10%), the system determines the sensor signal is implausible.

This fault triggers the brake system limp-home mode, potentially causing a loss of electronic brake assist, a hard brake pedal, ABS/ESC deactivation, and illuminating multiple system warning lights.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i sensor connector corroded after water ingress

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Brake system warning light illuminated after driving through water. Read DTC C05D000. Found water inside the IPB harness connector (located above the left front wheel arch). Pins 3 and 4 (sensor A/B signals) had green corrosion. Cleaned the connector and applied conductive protectant; signal discrepancy temporarily cleared but returned after one week. Replaced the IPB harness connector and waterproofed the connection to completely eliminate the fault.
BYD DTC AI Analysis

Seal master cylinder position sensor internal drift

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Customer reported excessive free play at the beginning of brake pedal travel and a "Brake System Fault" warning on the dashboard. Live data showed sensor A voltage rising from 0.5V to 2.8V and sensor B from 0.5V to only 2.1V when depressing the pedal—a 25% difference (normal: <5%). Wiring checked normal, confirming an internal IPB sensor fault. Replaced the IPB assembly and completed calibration. The signal difference between the two channels returned to 1.2%, clearing the fault.
BYD DTC AI Analysis

Wiring harness wear on Qin PLUS caused intermittent fault

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ABS warning light illuminated intermittently on rough roads. DTC C05D000 stored as history code. Inspection revealed chafing on IPB-to-body harness transition at firewall mounting clip; Sensor B signal wire insulation worn through, intermittently shorting to shield. Repaired harness and re-secured routing. Fault did not recur over 50 km of continuous road testing.
BYD DTC AI Analysis

Yuan Plus: IPB replaced without calibration, causing fault

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The workshop replaced the IPB assembly without performing sensor zero-point calibration. After driving 10 km, the vehicle set fault code C05D000. Live data showed signal values of 0.3 V and 0.8 V for channels A and B respectively at standstill (theoretical value: 0.5 V ± 0.1 V). Executing 'Master Cylinder Position Sensor Zero-point Calibration' and 'Pedal Min/Max Position Learning' with a diagnostic scanner automatically cleared the fault code and restored normal system operation.
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.