AU
C059500

DTC C059500 indicates an abnormal internal power drive circuit or supply voltage in the IPB (Integrated Power Brake) system — Qin Plus

Braking System

DTC C059500 indicates an abnormal internal power drive circuit or supply voltage in the IPB (Integrated Power Brake) system.

This fault involves abnormal electrical performance of the power management unit (PMU) or DC-DC conversion circuit inside the IPB module, or the external power supply wiring.

The IPB controller triggers this DTC when it detects the internal drive voltage exceeds normal thresholds (typically below 9V or above 16V), excessive power supply ripple, or an abnormal internal drive MOSFET/IGBT circuit.

This fault can cause vacuum boost simulation failure, a hard brake pedal, energy recovery interruption, and restricted ESC/ABS functions.

In severe cases, the vehicle enters limp mode or fails to power up the high-voltage system.

This constitutes a critical driving safety fault.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Poor connection, oxidation, or corrosion in the IPB module power supply circuit (especially constant power B+ and ignition power IG1 circuits)
  • 2Blown dedicated IPB power supply fuse (usually 30A or 40A) in the engine compartment fuse box, or poor contact at the fuse holder.
  • 3Damaged IPB module internal power management chip, DC-DC converter circuit, or pre-driver circuit
  • 4Abnormal 12V battery voltage (undercharge, overcharge, or excessive voltage fluctuation) causes unstable IPB power supply.
  • 5Water ingress, terminal back-out, or a loose locking tab in the IPB wiring harness connector (32Pin or 48Pin) causes excessive contact resistance.
What To Do
  • 1
    Use the VDS/DTS diagnostic tool to read fault codes, confirm if the C059500 status is current or history, and record freeze frame data (voltage, temperature, vehicle speed).
  • 2
    Check the vehicle 12V battery voltage and condition. Confirm static voltage is ≥12.6V and charging voltage is 13.5-14.5V. Replace the battery if necessary.
  • 3
    Check the engine compartment fuse box. Measure the continuity and voltage drop of the IPB power supply fuse (e.g., F1/14, F4/09, depending on vehicle model). The voltage drop must be less than 0.1V.
  • 4
    Disconnect the IPB module wiring harness connector (located near the front compartment firewall). Check the pins for corrosion, backing out, water ingress, or burn marks. Clean the pins with electrical contact cleaner and apply conductive grease.
  • 5
    Measure the voltage to ground at the IPB connector power supply terminals (constant B+, IG1). Verify the voltage is within 9-16V and fluctuates less than 0.5V. Measure the ground resistance; it must be less than 1Ω.
  • 6
    Check the IPB high-voltage and low-voltage wiring harnesses for wear, pinching, or a short to the vehicle body.
  • 7
    If all external wiring is normal, the fault is in the IPB assembly internal power drive circuit. Replace the IPB integrated brake booster assembly (part numbers vary by model, e.g., Song PLUS DM-i uses the 3535100-00 series).
  • 8
    After replacement, perform the brake system bleeding procedure: first perform standard bleeding (wheel cylinder bleeding), then perform deep bleeding (IPB internal hydraulic line bleeding).
  • 9
    Use the diagnostic tool to perform IPB module calibration, including Zero Point Calibration and Brake Pedal Travel Learning.
  • 10
    Clear the fault code and perform a road test (including low- and medium-speed braking and energy recovery conditions). Verify the fault light is off and brake assist operates normally.
Real-World Cases
BYD DTC AI Analysis

Blown fuse causes IPB power supply abnormality in Song PLUS DM-i

✓
Vehicle failed to engage high voltage. Instrument panel displayed "Brake System Fault" and "Check Powertrain". VDS read current fault code C059500. Checked the engine compartment fuse box and found the IPB 30A fuse blown; the replacement blew immediately. Measured resistance from the IPB supply terminal to ground and found an intermittent short (fluctuating around 50Ω). Diagnosed IPB internal power module breakdown. Replaced the IPB assembly and fuse, performed brake bleeding and calibration. Fault cleared.
BYD DTC AI Analysis

Loose wiring harness connector causing intermittent fault in Seal EV

✓
Owner reported intermittent "Braking System Fault" warnings on the instrument cluster while driving. Warnings cleared after restarting and occurred 2-3 times daily. Shop inspection found stored DTC C059500. The IPB wiring harness 32-pin female connector had pin retraction on power pins 12 and 13; male terminals showed minor oxidation. Water ingress into the front compartment had deteriorated the connector seal. Technicians extracted and reseated the pins using a dedicated extraction tool, cleaned the connector, reapplied waterproof conductive grease, and secured the harness retaining clips. One-week follow-up confirmed the fault has not recurred.
BYD DTC AI Analysis

Han EV auxiliary battery drain caused C059500 and linked faults

✓
After 5 days parked, vehicle failed to start. Jump-started; multiple dash warnings appeared. Scanned codes: C059500 (brake booster power supply abnormal), U0146 (communication fault with IPB). 12V battery measured 8.2V, 23% health. Replaced battery, cleared codes; C059500 did not return. Root cause: Severe discharge dropped IPB supply voltage below 9V threshold, triggering power anomaly protection. Check parasitic draw or replace battery.
BYD DTC AI Analysis

BYD Qin PLUS DM-i IPB internal driver board damaged

✓
The brake pedal suddenly went stiff, requiring heavy effort to depress. The ABS and ESC warning lights stayed on. The scan tool showed code C059500 (current and cannot be cleared). Checked supply voltage at 12.8V – normal. Ground – normal. CAN bus voltage around 2.5V – normal. Disassembled the IPB assembly and inspected the internal circuitry. Found the output capacitor on the DC-DC chip (typically TPS or Infineon series) on the power driver board was bulging, with unstable output voltage fluctuating between 5-8V. Replaced the IPB assembly. Fault resolved, brake assist returned to normal.
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.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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.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.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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.