AU
C058800

DTC C058800 indicates the signal voltage of the brake booster Motor Position Sensor (MPS) inside the Integrated Power Brake (IPB) electro-hydraulic module falls below the ECU threshold (typically below 0 — Atto 8

Braking System

DTC C058800 indicates the signal voltage of the brake booster Motor Position Sensor (MPS) inside the Integrated Power Brake (IPB) electro-hydraulic module falls below the ECU threshold (typically below 0.5V or 10% of the reference voltage).

The sensor uses electromagnetic or Hall effect principles to monitor the booster motor rotor position in real time, enabling closed-loop control of the motor torque output and brake assist level.

When the ECU detects the sensor voltage remains continuously below the calibrated value, it sets a circuit undervoltage fault.

This fault prevents the IPB system from accurately determining the motor position, which limits or disables the electric brake assist function.

As a result, the vehicle may enter Limp Home Mode, the brake pedal becomes hard, and the ESC/ABS warning lights illuminate.

The C058800 fault code on the Atto 8 indicates low voltage from the brake booster motor position sensor inside the Integrated Power Brake module. This is a medium-severity fault that can reduce or disable electric brake assist, making the pedal hard and triggering ABS/ESC warnings. Common causes include a failed sensor or wiring/connector short to ground. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Motor position sensor internal short circuit or component aging: a short circuit in the sensor's internal coil or a damaged Hall element pulls the output voltage low.
  • 2Wiring harness short to ground or connector fault: Damaged sensor wiring harness insulation causes a short to the vehicle body, or water ingress, oxidation, or loose connector pins cause excessive contact resistance.
  • 3Abnormal IPB module internal power supply circuit: Internal 5V reference voltage regulator failure or filter capacitor short circuit, causing insufficient sensor supply voltage.
  • 4Sensor signal wire chafing: Wiring harness rubs against a metal edge of the vehicle body. Long-term vibration wears through the wire insulation, causing a short to ground.
  • 5Extreme low temperature or electromagnetic interference: Although rare, sensor characteristic drift in extreme environments or strong electromagnetic interference may trigger a momentary false undervoltage fault.
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS or X-431 to read DTC C058800 and freeze frame data. Record parameters such as vehicle speed, voltage, and temperature at the time of the fault. Confirm whether the fault is current (Current) or historical (History).
  • 2
    Visual and connector inspection: Check the IPB module exterior for impact damage and leaks. Disconnect the IPB wiring harness connector and check the pins for corrosion, backed-out pins, and signs of water ingress. Test the connector sealing.
  • 3
    Sensor supply voltage measurement: With Key-ON, measure the voltage to ground at the motor position sensor supply pin on the IPB connector (typically the 5V reference voltage). Standard value: 4.8-5.2V. If below 4.5V, check the module internal power supply circuit.
  • 4
    Signal line voltage and continuity check: Measure the voltage at the sensor signal feedback pin. Normal voltage varies continuously between 0.5-4.5V. If the voltage is 0V, measure the wiring harness continuity from the IPB to the sensor (internal) and the insulation resistance to ground. Insulation resistance must be greater than 10MΩ.
  • 5
    Dynamic signal monitoring and load testing: Use an oscilloscope to monitor the sensor signal waveform while operating the brake pedal. Check for signal interruptions or voltage drops. Perform a road test and observe if the fault recurs under specific conditions (such as hard braking or bumps) to rule out intermittent poor contact.
  • 6
    IPB assembly replacement and calibration: If diagnostics confirm an internal sensor or module circuit fault (the sensor typically integrates with the IPB and cannot be replaced separately), replace the IPB electro-hydraulic module assembly. After replacement, perform the bleeding procedure, sensor zero-point calibration, and ESC function test.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i brake booster failure after wading

✓
After driving through flood water, the instrument cluster displayed "Braking System Fault". Scanning showed DTC C058800. Found the IPB module in the left front wheel arch. The connector waterproof seal had deteriorated, letting water in to oxidise the pins and create a 0.8kΩ short between the sensor supply pin and ground. Cleaned and dried the connector, applied conductive grease, and temporarily cleared the fault, but it returned after one week. Replaced the IPB wiring harness connector and sealed it properly to permanently fix the issue.
BYD DTC AI Analysis

Wiring harness wear causes intermittent low voltage

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When driving on rough roads, the brake pedal intermittently hardened and DTC C058800 appeared. Static voltage measurements normal. Found the IPB-to-body harness loose at the firewall penetration; vibration wore through the insulation, exposing copper wires that shorted to ground. Rewrapped the harness, adjusted the clip positions, and ensured 10 mm or more clearance from the body. The fault has not reoccurred.
BYD DTC AI Analysis

Replaced IPB module assembly due to internal sensor failure.

✓
Vehicle started with ABS warning light on; DTC C058800 present. External harness power supply measured 5.02V (normal). Signal wire showed continuity to ground (abnormal). Disconnected external harness and measured IPB internal sensor pins directly: still showed short to ground (<1Ω). Determined IPB internal motor position sensor coil short. Replaced IPB electro-hydraulic module assembly, bled brake system, performed ESC calibration and cleared DTC. Assist function restored.
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
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.