AU
C054200

DTC C054200 indicates an electrical signal fault in Pressure Sensor 2 within the IPB (Integrated Power Brake) — Seal U

Braking System

DTC C054200 indicates an electrical signal fault in Pressure Sensor 2 within the IPB (Integrated Power Brake).

This sensor typically provides the master cylinder pressure sensor secondary signal or monitors wheel cylinder pressure.

The sensor transmits real-time brake pressure data to the IPB-ECU using a 0.5-4.5V analog voltage signal or a PWM digital signal.

The ECU logs a short circuit (to ground or power) or an open circuit if the sensor signal voltage remains outside the valid threshold (typically below 0.25V or above 4.75V) for over 200ms.

As the BYD IPB utilizes a Brake-by-Wire architecture, the pressure sensor signal serves as a key parameter for calculating brake force distribution, triggering ABS/ESC intervention, and coordinating electro-hydraulic braking with energy recovery.

This fault triggers the IPB fail-safe mode, disabling ESC, AEB, Auto Hold, and brake energy recovery.

The system retains only basic hydraulic brake assist, increasing the risk of extended braking distances.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1IPB assembly internal pressure sensor 2 is damaged, has a cold solder joint, or has a ruptured diaphragm (primary failure mode; the sensor integrates into the IPB housing and is not serviceable separately).
  • 2IPB wiring harness connector (32-pin or 48-pin, depending on vehicle model): terminal back-out, poor contact, or seal failure causing water ingress and corrosion, resulting in an intermittent open circuit or short to ground in the signal line.
  • 3The low-voltage signal wiring harness chafes in the high-temperature area of the engine compartment or at the firewall pass-through. The damaged insulation causes a short to body ground, or contact with the 12V power wiring harness causes a short to power.
  • 4A fault in the IPB internal 5V reference voltage power supply module (ECU supplying power to the sensor) causes abnormal Sensor 2 operating voltage, indirectly triggering an out-of-range signal.
  • 5Under extreme operating conditions (such as severe collisions or wading), abnormal pressure pulsation inside the IPB hydraulic valve body causes fatigue fracture of the solder joints at the sensor electrical connector.
What To Do
  • 1
    Safety preparation: Turn off the ignition and power down the vehicle. Disconnect the 12V battery negative terminal and wait at least 3 minutes for the high-voltage capacitors inside the IPB to discharge completely. Wear insulated protective equipment.
  • 2
    Visual inspection: Inspect the IPB assembly (located near the left shock absorber tower in the engine compartment or at the firewall) for physical damage or brake fluid leaks. Verify wiring harness connector X1 (main connector) is fully locked, the sealing ring is intact, and there are no signs of water ingress (green corrosion on pins) or burn marks.
  • 3
    Initial diagnostic scan: Connect VDS 2000 or the BYD dedicated diagnostic tool. Read the freeze frame data to confirm if C054200 is a current (Active) or historical fault. Check if 'Pressure Sensor 2 Voltage' in the data stream displays 0V, 5V, or 'Invalid' (voltage normally varies between 0.5-4.5V with pedal travel).
  • 4
    Harness continuity and insulation test: Disconnect the IPB connector. Use a multimeter to measure the resistance from the Pressure Sensor 2 signal pin (refer to the circuit diagram, usually Connector X Pin Y) to ground (should be >1 MΩ, otherwise short to ground), the resistance to +B (12 V) (should be >1 MΩ, otherwise short to power), and the continuity resistance from the signal pin to the corresponding pin at the ECU (should be <0.5 Ω, otherwise open circuit).
  • 5
    Sensor dynamic test: Reconnect the connector. Monitor the signal wire voltage using an oscilloscope. Press the brake pedal and verify the voltage rises smoothly without jumps. If the voltage remains at an extreme value or jumps, and the circuit test is normal, the IPB internal sensor is faulty.
  • 6
    Component replacement and matching: If diagnostics confirm an internal IPB fault, replace the IPB assembly with ECU (verify the part number matches the vehicle configuration, such as Bosch IPB version 9.0 or 9.3). After replacement, perform the following: a) Brake system bleeding procedure (use a diagnostic tool to trigger motor pump bleeding); b) IPB coding configuration; c) Longitudinal acceleration sensor and steering angle sensor calibration.
  • 7
    Function verification: Clear the fault code, run the IPB self-check (Auto-Test), and confirm C054200 does not recur. Perform a road test to conduct a low-speed (20 km/h) ABS activation test and ESC intervention test. Confirm no abnormal warnings occur and the brake pedal feel is normal.
Real-World Cases
BYD DTC AI Analysis

2021 Song PLUS DM-i: ESC warning light on after driving through water

✓
A Song PLUS DM-i with 30,000 km developed simultaneous ABS, ESC and auto hold warning lights on the instrument cluster after wading through heavy rain floodwater. VDS retrieved codes C054200 (current fault) and C003F00 (lateral acceleration sensor fault, intermittent). Inspected IPB connector X1: seal ring degraded, water inside, Pin 12 (pressure sensor 2 signal) showed green copper corrosion. Repair: Cleaned connector with electronic contact cleaner, replaced waterproof seal ring, applied conductive grease and reset. Cleared fault codes, road tested OK, monitored one week with no recurrence. Replace IPB wiring harness connector if corrosion is severe.
BYD DTC AI Analysis

2022 BYD Dolphin: Intermittent warning after accident repair

✓
After front-end collision repairs, the owner reported intermittent brake system warnings on the instrument cluster, especially on rough roads. VDS showed C054200 as a historical fault. Checked the IPB wiring harness and found the retaining clips were not reinstalled during the collision repair, letting the harness rub against the metal edge of the engine compartment firewall. The insulation wore through to bare copper, causing an intermittent short to ground on the pressure sensor 2 signal line. Repaired the harness by cutting out the damaged section, soldering the joint, and sealing with heat-shrink tubing. Rerouted the harness, added protective corrugated tubing, and secured it to the original mounting points. Fault resolved.
BYD DTC AI Analysis

BYD Yuan Plus (new vehicle): Pressure sensor 2 internal drift

✓
A one-month-old Yuan PLUS suddenly displayed "Braking System Fault" during normal driving. VDS read code C054200. Live data showed Pressure Sensor 2 voltage locked at 0.03V (short-to-ground value), but with the connector disconnected, the harness side measured normal 5V reference voltage. Diagnosed as internal IPB Sensor 2 failure or ECU sampling circuit fault. Replaced the IPB assembly (with ECU) under warranty. After replacement, performed brake bleeding and calibration. Fault cleared. Analysis: supplier batch issue, cold solder joints inside the sensor.
BYD DTC AI Analysis

2021 Han EV — Signal interference from modifications

✓
After the owner installed a high-power amplifier and ambient lighting, fault code C054200 set. Inspection found the modified wiring drew power directly from the battery, with unshielded power cables bundled parallel to the IPB signal harness. High-power device operation generated electromagnetic interference, causing pressure sensor 2 signal voltage to momentarily exceed limits. Fix: Removed unnecessary modified wiring sections running parallel to the IPB harness, replaced high-power device power cables with independently shielded lines routed well away from the body control module wiring, and cleared the code. Fault has not returned.
BYD DTC AI Analysis

BYD Qin PLUS DM-i warning after long-term parking

✓
After three months parked in an underground garage, the vehicle showed a brake system fault at startup. VDS reported codes C054200 and C003700 (low brake fluid level, historical fault). Inspection found the brake fluid slightly below the MIN line from natural depletion, plus minor oxidation on the IPB connector pins from the damp environment. Topped up DOT4 brake fluid to the MAX line, cleaned the connector pins, applied electronic protectant, and ran the IPB function test. Analysis: Low fluid level caused abnormal internal pressure balance in the IPB. Extended stationary time pushed the sensor signal deviation beyond the threshold, triggering fault protection.
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.