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+) — Qin Plus

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.

The C050900 fault code on the Qin Plus indicates a high-severity short circuit in the right front wheel speed sensor signal circuit, often causing ABS, ESP, and braking warnings. Common causes include damaged wiring from rubbing near the wheel arch or suspension, or water ingress/corrosion in the sensor connector. Stop driving if braking feels abnormal and visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 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 against the body bracket, steering knuckle, or suspension components. Prolonged friction damages the insulation, causing the power and signal wires to contact and short circuit.
  • 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.
  • 3Wiring harness crushed, bent, or improperly secured during front-end accident repairs or vehicle modifications (such as installing mud flaps or modifying brakes), damaging and exposing the internal copper core.
  • 4A damaged front wheel bearing or incorrect sensor installation gap causes the sensor head to rub against the magnetic ring and overheat, resulting in an internal circuit breakdown and 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 signal line reverse breakdown.
What To Do
  • 1
    Connect the BYD VDS diagnostic tool and confirm C050900 is a Current DTC. Read the IPB data stream and check if the right front wheel speed signal displays a fixed high value (e.g., 8191 rpm or maximum value) or zero. Compare this reading with the other three wheels to confirm the abnormality.
  • 2
    Raise the vehicle to a suitable height. Visually inspect the right front wheel speed sensor connector for looseness, water ingress, and oxidized or deformed pins. Inspect the wiring harness securing and visual integrity at the fender liner, front wheel arch, below the A-pillar, and firewall pass-through. Verify the clearance between the wiring harness, body metal edges, and suspension mounting bolts.
  • 3
    Disconnect the right front wheel speed sensor connector. Use a multimeter to measure the voltage between the power supply pin (usually brown or red wire) and ground; verify it reads 12V battery voltage. Measure the voltage between the signal pin (usually yellow/green or white/green wire) and ground. The reading should normally be 0V or a pulse voltage. If the voltage remains at 12V, the signal wire is shorted to power.
  • 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 the sensor-side power and signal pins show continuity, replace the sensor.
  • 5
    Inspect the wiring harness section by section: starting from the sensor connector and working toward the body harness, gradually open the corrugated conduit. Focus on harness bends, retaining clips, and pass-through holes. After locating the short circuit, 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 tip, and verify no interference between the sensor and wiring harness.
  • 7
    After repair, clear the fault codes and perform a road test (including straight-line driving, turning, and bumpy roads). Observe the four-wheel speed data stream via VDS to verify the values are synchronized and reasonable. Confirm the ABS and ESP warning lights turn off and 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 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.