AU
C1205

DTC C1205 indicates the ABS/ESC control module continuously detects 0 V (no signal state) from the right front wheel speed sensor — Qin Plus

Braking System

DTC C1205 indicates the ABS/ESC control module continuously detects 0 V (no signal state) from the right front wheel speed sensor.

In BYD new energy vehicles, the control module logs an open circuit or sensor failure because the variable reluctance or Hall-effect sensor fails to transmit a valid sine or square wave signal to the ECU.

This fault forces the Anti-lock Braking System (ABS), Electronic Stability Control (ESC), Automatic Emergency Braking (AEB), Auto Vehicle Hold (AVH), and energy recovery systems into a degraded or failed mode, and illuminates the ABS/ESC warning lamps on the instrument cluster.

Unlike DTC C1204 (excessive signal variation/intermittent fault), C1205 represents a continuous signal loss, typically indicating a hard circuit fault or a damaged sensor.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Right front wheel speed sensor internal coil open circuit, burnt Hall element, or internal circuit fault (infinite resistance or 0 Ω)
  • 2Sensor wiring harness chafing or breakage in high-vibration chassis areas (such as near the suspension control arm), or poor contact due to oxidized connector terminals, terminal back-out, or water ingress corrosion.
  • 3Worn or loose wheel hub bearing causing the gap between the sensor and tone ring (magnetic ring) to exceed specification (normal: 0.3-1.2 mm), or a loose sensor mounting bolt causing sensor displacement.
  • 4Tone ring damaged, missing teeth, severely deformed, or excessive ferromagnetic metal debris accumulated on its surface shields the magnetic circuit.
  • 5Internal fault in the ABS control module signal processing circuit (signal input port shorted to ground or damaged sampling resistor; low probability)
What To Do
  • 1
    Connect the VDS diagnostic tool and read the DTC freeze frame. Confirm the right front wheel speed data stream remains at 0 km/h and the DTC does not clear, ruling out intermittent interference.
  • 2
    Raise the vehicle and visually inspect the right front sensor, wiring harness sleeve, and connector for damage, water ingress, oil contamination, or signs of physical impact.
  • 3
    Disconnect the sensor connector. Use a multimeter to measure the sensor resistance (magnetic inductive standard value: approx. 1.0-1.5kΩ@25℃; Hall type requires a powered test). Replace the sensor if the resistance is abnormal.
  • 4
    Check the sensor installation torque (standard 8-10 N·m). Use a feeler gauge to measure the clearance between the sensor tip and the tone ring tooth crest (0.3-1.2 mm). Inspect the tone ring for missing teeth, cracks, or attached foreign matter.
  • 5
    Measure wiring harness continuity: From the sensor connector to the ABS pump connector, measure the resistance of the power (B+, 12V), signal (SIG), and ground (GND) circuits (must be <1Ω) and their insulation resistance to ground and power (must be >10MΩ).
  • 6
    Verify by substitution: Swap the right-front and left-front sensors. Perform a road test and observe if the fault code transfers to the left-front to confirm a fault in the sensor itself.
  • 7
    Inspect the ABS pump connector terminals for oxidation or backed-out pins. Measure the internal resistance of the corresponding ABS pump pins. If the circuit is normal but receives no signal input, the ABS control module is faulty. Replace the ABS assembly and calibrate the yaw rate sensor.
Real-World Cases
BYD DTC AI Analysis

BYD E2 right front wheel speed sensor wiring harness worn through, open circuit

✓
A 2019 BYD E2 with 60,000 km showed ABS/ESC warning lights. Retrieved DTC C1205. Inspection found the right front sensor connector-to-body harness near the steering knuckle had boot damage from long-term steering friction, and the copper core wire was completely severed. Cut out the damaged harness section, re-soldered the wiring using waterproof heat-shrink tubing, and secured the harness routing to prevent suspension interference. Fault cleared.
BYD DTC AI Analysis

Yuan EV wheel hub bearing wear caused excessive sensor gap.

✓
2020 BYD Yuan EV presented with DTC C1205. Live data showed right front wheel speed stuck at zero. Sensor resistance measured normal and wiring continuity tested good, but the sensor-to-reluctor ring air gap measured 3.5 mm—severely out of specification. Further inspection found the right front wheel hub bearing worn and loose, allowing the reluctor ring to drop. Replaced the wheel hub bearing assembly (including the reluctor ring), restoring the air gap to 0.8 mm. Cleared the fault code; ABS function returned to normal.
BYD DTC AI Analysis

E1 sensor connector corroded by water ingress

✓
BYD E1 developed a C1205 fault after fording water. Removed the right front wheel speed sensor connector and found the internal terminals severely oxidised and white with electrolytic corrosion. The connector seal ring had aged and failed, letting water in during the crossing and shorting the signal terminal to ground. Cleaned the connector with precision electronic cleaner, replaced the seal ring and terminals, applied conductive grease. Fault resolved.
BYD DTC AI Analysis

E3 wheel speed sensor internal open circuit

✓
A 2020 E3 logged C1205 after accident repairs to the right front wheel. Sensor resistance measured infinite, indicating an open circuit in the internal coil. Replaced the sensor with a genuine part; fault remained. Further inspection found the accident had deformed the sensor mounting hole, causing the new sensor to twist under stress and fracture internally. Replaced the steering knuckle, reinstalled the sensor, and completely resolved the fault.
BYD DTC AI Analysis

Song EV reluctor ring accumulated metal debris causing signal shielding

✓
Following brake system repairs on a 2019 Song EV, the vehicle set DTC C1205. Checked the right front sensor and wiring—both were normal. Found the tone ring surface coated with ferromagnetic powder from brake pad wear, creating a magnetic shield that prevented the sensor from detecting the ring's magnetic field changes. Cleaned the metal debris from the tone ring surface and thoroughly cleaned it with carburetor cleaner. Signal returned to normal; cleared the fault code.
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.