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C059900

This fault code indicates the EPB (Electronic Parking Brake) control module detects an uncalibrated system, a communication fault, or an actuator fault — Atto 3

Braking System

This fault code indicates the EPB (Electronic Parking Brake) control module detects an uncalibrated system, a communication fault, or an actuator fault.

Although some repair data categorizes this code under the IPB (Integrated Power Brake) system, C059900 typically indicates interrupted CAN communication between the EPB control unit and the left and right rear parking motors, an unstable power supply, or lost internal module calibration data.

When this fault occurs, the EPB control module cannot accurately acquire motor position signals or execute control commands, causing partial or complete electronic parking brake failure.

Symptoms include the inability to release or apply the parking brake, and instrument cluster warnings.

Extreme cases compromise driving safety.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Wiring harness break caused EPB failure in BYD Qin Pro EV

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Symptoms: After starting the vehicle, the instrument cluster displayed "Check Electronic Parking Brake System". The EPB switch failed completely, the parking brake would not release, and the vehicle was immobilised. Diagnosis: VDS retrieved DTC C059900 along with C059801. The EPB module had normal power and earth. Found internal wire fracture in the right rear EPB motor harness at the right rear door hinge (outer insulation intact), cutting power to the motor. Repair: Cut out the damaged harness section, resoldered the wires, and fitted waterproof insulation sleeving. Rerouted the harness to avoid interference. Cleared the codes and performed EPB initialisation. Function restored.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro DM — Low battery voltage triggered system protection

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Symptoms: Electronic parking brake warning light occasionally illuminates while driving. Intermittent no-start after parking, more common on cold starts. DTC C059900 stored. Diagnosis: Measured static battery voltage at only 11.2V (capacity degraded to 60%). Inspected EPB control module ground point G106 and found loose bolt with oxidised contact surface, causing voltage instability that triggered protection. Solution: Replaced the degraded battery. Removed ground point G106, sanded off the oxidation, applied conductive paste, and tightened to specified torque (8–10 N·m). Cleared fault codes and road-tested one week without recurrence.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM control module internal fault

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Symptoms: While driving at high speed, the instrument cluster suddenly displayed "Electronic Parking System Fault". The vehicle continued to drive normally, but after stopping, the electronic parking brake function failed completely with no response from the switch. Diagnosis: Retrieved DTC C059900 which could not be cleared. Inspected the EPB control module (located beneath the centre console) and found cracks in the housing. Disassembly revealed water ingress had corroded the internal circuit board and shorted the integrated circuits. Resolution: Replaced the electronic parking brake control module with a new unit (part number: 3H-3600100). Performed EPB system matching with a diagnostic scan tool (entering the VIN and tyre specification parameters). Executed the motor bedding-in procedure (5 tighten-release cycles for each wheel).
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BYD DTC AI Analysis

BYD Han EV rear parking brake motor jammed

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Symptoms: EPB warning triggered when parking. Left rear wheel made clicking noise. Parking brake failed to release fully. Vehicle dragged when driving. DTC C059900 displayed. Diagnosis: Lifted vehicle. Left rear EPB motor ran with abnormal noise but brake caliper did not move. Removed motor and applied direct power: motor spun but output shaft had no torque. Internal worm gear worn and jammed. Data stream showed left rear motor current consistently above 20A (normal <8A), triggering overheat protection. Resolution: Replaced left rear EPB motor assembly (motor and cable). Adjusted cable preload during installation (free play 1–2mm). Performed EPB initialization after replacement: ignition ON → depress brake pedal → pull and hold EPB switch for 5 seconds → release switch → wait 10 seconds for self-learning.
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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.