AU
C058900

DTC C058900 indicates the IPB (Intelligent Integrated Braking System) electro-hydraulic control module detected a brake booster motor position sensor signal voltage exceeding the calibrated upper limit (typically >4 — Seal U

Braking System

DTC C058900 indicates the IPB (Intelligent Integrated Braking System) electro-hydraulic control module detected a brake booster motor position sensor signal voltage exceeding the calibrated upper limit (typically >4.8V or 95% of the reference voltage).

Typically a Hall-effect or electromagnetic position sensor, this component monitors the booster motor rotor position/travel in real time to enable precise electronic brake assist control (similar to a brake-by-wire i-Booster system).

Excessively high voltage saturates the signal at the ECU, preventing it from identifying the actual motor position.

This triggers fail-safe mode: the system disables the electronic assist function, the brake pedal becomes hard (mechanical backup remains available), and the ABS/ESC/brake system warning lamps illuminate.

This is a hard fault; once triggered, it remains active and does not self-clear.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Sensor signal circuit shorted to power (+12V or +5V reference voltage): Damaged wiring harness insulation contacts a body power wire, pulling the signal voltage high.
  • 2Motor position sensor internal short circuit or damage: Sensor Hall element breakdown causes an internal short between the signal terminal and reference voltage terminal.
  • 3IPB control unit (ECU) internal sampling circuit fault: analogue-to-digital converter (ADC) front-end protection diode breakdown or voltage divider resistor open circuit, causing abnormal sampling voltage.
  • 4Water ingress or corrosion in the sensor connector: An electrolytic conductive path forms between the plug pins, especially after vehicle washing or wading, causing an abnormal resistance drop between the signal wire and power wire.
  • 5Bent pins due to improper repair procedures: During removal and installation of the IPB assembly, the motor position sensor connector pins bend and contact the metal housing or adjacent power supply pins.
What To Do
  • 1
    Safety preparation and initial inspection: Disconnect the high-voltage Manual Service Disconnect (MSD) and wait 5 minutes for capacitor discharge. Use VDS2000 or Launch X431 to read all DTCs. Confirm if C058900 appears alone or alternates with C058800 (voltage too low) or other codes. Inspect the IPB electro-hydraulic module exterior for impact damage or fluid leaks. Check the motor position sensor connector (typically on the side of the IPB assembly) for looseness or water ingress.
  • 2
    Voltage measurement and wiring inspection: Reinstall the MSD, turn the ignition ON (do not press the brake pedal), and measure the sensor signal wire voltage without disconnecting the connector (normal voltage is 0.5-4.5V, varying with position). If the voltage is >4.8V or close to the reference voltage (5V), disconnect the sensor connector and measure the resistance between the harness-side signal wire and ground. Continuity indicates a short to ground. Measure the resistance between the signal wire and the power wire. Continuity confirms a short circuit in the wiring harness. Also verify the ECU outputs a stable sensor reference voltage (+5V).
  • 3
    Sensor body inspection: Remove the motor position sensor (usually integrated with the assist motor or mounted on the motor end cover) and measure the sensor resistance. Resistance between the signal terminal and ground, and between the signal terminal and power supply terminal must be >10MΩ (open circuit). Low resistance indicates an internal sensor short circuit. Observe the signal waveform using an oscilloscope. A normal signal shows a square wave or analog voltage that changes with motor rotation. If the signal line remains at 5V, the sensor is faulty.
  • 4
    IPB Control Unit Inspection: After verifying the wiring harness and sensor are normal, measure the resistance to ground at the ECU signal input pin. An abnormally low resistance indicates a damaged ECU internal sampling circuit. Check the IPB assembly connector for backed-out pins or enlarged terminal holes. If necessary, measure the wiring harness continuity between the ECU and the sensor (resistance should be <1Ω).
  • 5
    Component replacement and system calibration: Replace the faulty sensor or IPB assembly (ECU damage usually requires replacing the entire IPB module). After installation, perform: ① Brake system bleeding (use the diagnostic tool to activate the motor pump); ② Motor position sensor zero-point calibration (perform 'Brake Booster Position Learning' using VDS2000); ③ Longitudinal acceleration sensor calibration; ④ Road test to verify the brake assist function returns to normal and the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i brake booster failure after water ingress (wiring harness short circuit)

✓
After driving through flooded roads, the ABS/ESC warning lights illuminated on the dashboard and the brake pedal became stiff. Scanner read code C058900. Found the IPB electro-hydraulic module above the left front wheel arch. The motor position sensor plug seal had deteriorated; water entering the plug after wading shorted signal pin (Pin2) to reference voltage pin (Pin1) (measured resistance: 2.3kΩ). Cleaned and dried the plug, applied conductive grease, and replaced the seal. Fault cleared. Recommend checking plug waterproofing on vehicles from the same production batch.
BYD DTC AI Analysis

C058900 won't clear after accident repairs (bent pin)

✓
Front-end collision. After replacing the front bumper wiring harness, DTC C058900 set. Troubleshooting found the technician bent the signal pin (normally the center pin) when installing the IPB motor position sensor connector, causing it to contact the connector housing (ground) and the adjacent +5V reference voltage pin simultaneously and create a short to power. Repaired the pin and reconnected. Performed the brake booster position learning procedure (requires ignition on, brake pedal released, trigger motor zeroing via scan tool). Fault resolved.
BYD DTC AI Analysis

IPB control unit internal sampling circuit damaged

✓
No accident history. Brake system warning light suddenly illuminated during normal use. Measured motor position sensor signal line voltage constant at 5.04V (reference voltage). Disconnected sensor and measured ECU signal input pin resistance to ground at only 320Ω (normal >10kΩ). Confirmed ECU internal signal sampling resistor or ground protection circuit damage. Replaced IPB electro-hydraulic assembly (ECU integrated with assembly, no separate ECU available). Performed brake system bleeding and sensor calibration. Fault cleared. Analysis of the old part revealed ECU internal sampling chip overheated and burnt out, possibly related to prolonged braking during high summer temperatures.
BYD DTC AI Analysis

Thermal breakdown of the Hall element in the sensor body

✓
Vehicle set code C058900 after long-distance summer driving. The fault cleared after a cold restart but returned at operating temperature. At operating temperature, resistance between the sensor signal output and power supply terminals decreased as temperature rose, measuring only 5kΩ at 80°C. The Hall sensor had internal thermal instability; high-temperature leakage current pulled the signal voltage high. Replaced the motor position sensor (some models allow separate replacement; others require the complete motor assembly). Replacement resolved the fault. Inspect the motor cooling air duct for blockages.
BYD DTC AI Analysis

Aftermarket modification caused signal interference and false positives (reference case)

✓
Derivative case similar to C-series sensor faults: The owner fitted an aftermarket dashcam, tapping power from the IPB system supply circuit and causing voltage fluctuations. C058900 did not trigger directly, but C058A00 (out of range) occurred. Another C058900 case involved installing high-power radio equipment (vehicle transceiver) with the antenna near the IPB wiring harness; electromagnetic interference caused the ECU to misread signal voltage as excessive. Removing the aftermarket equipment and recalibrating resolved the issue. Ask about modification history during diagnosis.
Other Seal U 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.