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C059100

This DTC indicates the supply voltage to the IPB (Integrated Power Brake) internal brake booster motor is below the normal operating threshold set by the ECU (typically below 9V or 75% of the nominal value) — Atto 3

Braking System

This DTC indicates the supply voltage to the IPB (Integrated Power Brake) internal brake booster motor is below the normal operating threshold set by the ECU (typically below 9V or 75% of the nominal value).

The IPB system uses a vacuum-free electro-hydraulic assist design.

A DC motor drives a hydraulic pump to build brake assist pressure.

When motor voltage drops too low, the ECU limits assist torque output to protect hardware.

This results in a significantly harder brake pedal, longer pedal travel, and increased braking distance.

The IPB internal power management module triggers this fault by monitoring the motor drive circuit voltage in real time.

Possible causes include an abnormal external power supply, excessive wiring voltage drop, poor connector contact, or a failed IPB internal DC-DC converter or motor drive circuit.

A persistent fault causes the IPB to enter Limp Home mode, limits vehicle speed, and illuminates multiple system warning lights.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Song PLUS DMi: Water ingress and corrosion in IPB connector after wading caused low voltage

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After driving through water, the instrument panel showed ABS/ESC warning lights. Read DTC C059100 (brake booster motor voltage low). Found the IPB mounted beneath the left front chassis rail with a perished connector seal; inside showed water staining and green corrosion. Disassembled the connector, cleaned the pins with ethanol, applied conductive grease and replaced the seal. Motor supply voltage returned to normal. Cleared the fault codes and road-tested for one week with no recurrence.
BYD DTC AI Analysis

Sudden brake pedal hardening and power assist failure while driving.

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Owner reported brake pedal suddenly hardened during high-speed driving, requiring heavy effort to decelerate; brake system warning light illuminated. Scan tool read DTC C059100; freeze frame showed motor voltage at 7.2V during the fault. Found burn marks on IPB supply fuse F1/40A blades; fuse holder internal spring clips had lost elasticity, causing poor contact. Replaced fuse and holder, tightened ground point. Fault resolved.
BYD DTC AI Analysis

C059100 still present after replacing low-voltage battery on Yuan Plus

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Vehicle set DTC C059100. The shop replaced the 12V battery but the code remained. Deep inspection found soft breakdown in the IPB internal brake booster motor drive MOSFET, causing abnormal static current draw (normal <0.3A, measured 1.8A) that dragged system voltage low. Replaced the IPB assembly with ECU, bled the brakes and calibrated sensors. Motor operating voltage returned to 13.8V; fault completely resolved.
BYD DTC AI Analysis

Han EV IPB internal DC-DC converter intermittent fault

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Brake system warning light came on intermittently with DTC C059100. External power supply tested normal. Suspected internal IPB power management module failure. Disassembled IPB assembly (maintain dust/water protection). Found capacitor leakage around the DC-DC converter chip (typically Mornchip or TI solution) on the internal PCB, causing unstable output voltage. Replaced IPB assembly; fault cleared. Returned old part to factory for analysis.
BYD DTC AI Analysis

Qin PLUS DM-i wiring harness chafing against body causing intermittent low voltage

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While driving on rough surfaces, the brake warning light illuminated intermittently. The scan tool retrieved historic DTC C059100. Inspection revealed the IPB wiring harness rubbing against the sheet metal edge at the front left chassis rail; abraded insulation caused an intermittent short to ground on the power supply line, producing a voltage drop. Repaired the harness using double-layer heat shrink tubing, rerouted and secured the harness (added corrugated tube protection), and repositioned cable ties to avoid sharp edges. Fault resolved.
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.