AU
C050900

This DTC indicates a short circuit between the 12V power supply wire and the signal output circuit of the right front (FR) wheel speed sensor, or a direct short from the signal wire to battery positive (B+) — Seal U

Braking System

This DTC indicates a short circuit between the 12V power supply wire and the signal output circuit of the right front (FR) wheel speed sensor, or a direct short from the signal wire to battery positive (B+).

In the BYD IPB (Intelligent Integrated Braking System) architecture, the wheel speed sensor is typically a Hall-effect type.

Under normal operation, the supply voltage is 12V, and the signal wire outputs a 0.5-4.5V pulse voltage.

When the signal wire shorts to the 12V supply, the IPB control unit receives a continuous high-level signal and cannot identify wheel speed pulses.

This causes the system to lose the right front wheel speed data or display an abnormal fixed value.

This condition triggers the safety protection mechanisms of systems including ABS, ESP, and EHB (Electro-Hydraulic Braking), causing brake assist functions to degrade or fail.

Multiple warning lights illuminate on the instrument cluster, severely compromising driving safety.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1An improperly secured right front wheel speed sensor wiring harness at the fender liner, below the A-pillar, or at the front wheel arch rubs continuously against body brackets, the steering knuckle, or suspension components. This damages the insulation and causes a short circuit between the power wire and the signal wire.
  • 2Sensor connector seal failure allows water ingress after wading or high-pressure washing, causing electrolytic corrosion and short circuits between pins; or an improperly seated connector causes pin misalignment and poor contact.
  • 3Crushing, bending, or improperly securing the wiring harness during vehicle front-end accident repairs or modifications (such as installing mud flaps or modifying brakes) damages and exposes the internal copper core.
  • 4Damaged front wheel bearing or abnormal sensor installation gap causes the sensor head to rub against the magnetic ring and overheat, resulting in internal circuit breakdown and a short circuit.
  • 5Internal driver circuit fault in the IPB control unit (very rare), causing an abnormal increase in the supply voltage output to the sensor or reverse breakdown of the signal line.
What To Do
  • 1
    Connect the BYD VDS diagnostic tool and confirm C050900 is a current fault (Current DTC). Read the IPB data stream. Check if the right front wheel speed signal displays a fixed high value (such as 8191 rpm or maximum value) or zero. Compare this reading with the other three wheels to confirm the anomaly.
  • 2
    Raise the vehicle to a suitable height. Visually inspect the right front wheel speed sensor connector for looseness, water ingress, or oxidized and deformed pins. Check the harness mounting and visual integrity at the fender liner, front wheel arch, below the A-pillar, and firewall pass-through. Verify the clearance between the harness, body metal edges, and suspension mounting bolts.
  • 3
    Disconnect the right front wheel speed sensor connector. Use a multimeter to measure the voltage to ground at the power supply pin (usually the brown or red wire) and confirm it is 12V battery voltage. Measure the voltage to ground at the signal pin (usually the yellow/green or white/green wire). Normal voltage is 0V or a pulse voltage. A constant 12V confirms the signal wire is shorted to the power supply.
  • 4
    Keep the connector disconnected and measure continuity between the signal wire and the power wire. If continuity exists, the wiring harness has an internal short circuit. If no continuity exists, measure the sensor resistance. If continuity exists between the power and signal pins on the sensor side, replace the sensor.
  • 5
    Inspect the wiring harness section by section: starting from the sensor connector, gradually peel back the corrugated conduit toward the body harness. Inspect the harness bends, retaining clips, and pass-through holes. Locate the short circuit and repair it using insulating tape and heat-shrink tubing. If the harness is severely damaged, replace the entire front compartment wiring harness.
  • 6
    Inspect the right front wheel bearing magnetic ring for damage, measure the sensor installation gap (standard value: 0.3-1.2 mm), clean metal debris from the sensor head, and ensure no interference between the sensor and the wiring harness.
  • 7
    After completing the repair, clear the fault code and perform a road test (including straight-line driving, turning, and bumpy roads). Use VDS to monitor the four-wheel speed data streams to verify they synchronize and display reasonable values. Confirm the ABS and ESP warning lights are off and the systems function normally.
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i inner fender wiring harness chafed and shorted

✓
While driving, the ABS warning light suddenly illuminated and the instrument cluster displayed "Check Brake System". A VDS scan showed current fault code C050900. Lifted the vehicle and found the right front wheel speed sensor harness had detached from the retaining clip on the front fender liner, allowing it to sag and rub against the body bracket. The insulation wore through, shorting the power and signal wires together. The signal line measured constant 12 V. Repair: Stripped back the damaged harness, separately wrapped the power and signal wires, added corrugated tube protection, and re-secured the harness with cable ties to ensure at least 20 mm clearance from the sheet metal edges. Cleared the fault codes and road tested; all four wheel speed readings were normal, fault resolved.
Original source ↗
BYD DTC AI Analysis

Qin PLUS DM-i sensor connector corroded due to water ingress

✓
After driving through water, the ABS and ESP warning lights stayed on and the right front wheel speed read zero. The scan tool read DTCs C050900 and C050A00 (intermittent fault). Found obvious water stains and green copper corrosion inside the right front wheel speed sensor connector. Lowered insulation resistance between the pins caused a power-to-signal short. The connector seal had aged, letting water in during wading. Cleaned the connector with electronic cleaner, blew it dry with an air gun, applied conductive paste, and reconnected. Also checked the wiring harness corrugated tube for damage and repaired it to stop future water ingress. After the repair, advised the owner to avoid deep water.
Original source ↗
BYD DTC AI Analysis

Han EV front wheel arch wiring harness interference with steering knuckle

✓
ABS warning light illuminated intermittently on rough roads. DTC C050900 indicated intermittent fault. Harness appeared normal during static inspection, but dynamic interference showed between the right front wheel speed sensor harness and steering knuckle when turning the steering wheel with the vehicle raised. Found broken harness retaining clip; harness rubbed steering knuckle bolt during steering, damaging insulation and causing occasional shorts. Replaced clip, rerouted harness to clear moving parts, and repaired minor damage with heat shrink tubing. Ran steering lock-to-lock test and road test; confirmed no interference, fault resolved.
Original source ↗
BYD DTC AI Analysis

Dolphin IPB system wiring harness worn at firewall penetration

✓
e-Platform 3.0 (Dolphin) set DTC C050900 with DiPilot intelligent driving assist function restricted. Vibration wore through the harness protective sleeve at the engine bay firewall penetration, shorting the right front wheel speed sensor signal wire to the cabin 12V power line. This significantly impacts new energy vehicles because the wheel speed signal feeds both the IPB and vehicle control unit. Repaired the damaged harness, added flame-retardant corrugated tubing, and adjusted the harness fixing position. Also checked high-voltage system insulation resistance since the damage was near high-voltage components; confirmed no high-voltage leakage risk, cleared the DTC, and calibrated the intelligent driving assist system.
Original source ↗
BYD DTC AI Analysis

Tang DM wiring harness improperly secured after accident repair

✓
After front-end collision repairs, the vehicle threw C050900 immediately at startup. Inspection showed the shop had re-wrapped the harness inside the right front fender but chose mounting points poorly. The harness contacted metal burrs on the fender; driving vibrations chafed through the wiring and created a short. Repair: Rerouted the harness to avoid metal burrs and weld seams in the repaired area. Applied double-layer protection with fleece tape and corrugated tubing, and installed rubber grommets at critical mounting points. Cleared the code, ran ABS dynamic tests and verified ESC function. The fault did not return.
Original source ↗
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.