AU
C003504

DTC C003504 indicates a right front wheel speed sensor (RF Wheel Speed Sensor) circuit or signal abnormality, specifically low sensor supply voltage, signal voltage out of range, or compromised circuit integrity — Atto 8

Braking System

DTC C003504 indicates a right front wheel speed sensor (RF Wheel Speed Sensor) circuit or signal abnormality, specifically low sensor supply voltage, signal voltage out of range, or compromised circuit integrity.

In the BYD ABS/ESP system, this fault prevents the control unit from obtaining an accurate right front wheel speed signal and triggers limp mode.

Effects include: ABS function disabled, ESP deactivated, EBD malfunction, automatic emergency braking (AEB) function limited, regenerative braking efficiency reduced or disabled, and cruise control unavailable.

This DTC is a hard fault.

The control unit triggers this code upon continuously detecting the abnormality with the ignition switch in the ON position or while driving.

The C003504 fault code on the Atto 8 indicates a right front wheel speed sensor circuit or signal problem, often causing ABS, ESP, EBD, AEB, regenerative braking, and cruise control limitations. Severity is medium, but the fault can trigger limp mode. Common causes include a faulty wheel speed sensor or damaged, corroded, or loose wiring/connectors. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Wheel speed sensor component fault: Internal coil open/short circuit, abnormal magnetic induction sensor resistance (normal 1.0-1.5kΩ), abnormal Hall sensor power supply, or internal circuit damage causing weak or distorted signal output.
  • 2Wiring and connector issues: sensor plug oxidation, water ingress corrosion, loose pins; wiring harness insulation wear causing a short to ground or intermittent open circuit; high engine compartment temperatures causing wiring harness aging and cracking, especially prone to rubbing against the body where the right front longitudinal beam retaining clip is loose.
  • 3Abnormal mechanical installation and clearance: Sensor-to-signal tone ring (reluctor ring) clearance is too large (standard: 0.3-1.2 mm) or too small, causing scraping; excessive right front wheel bearing play or damage causes signal tone ring radial runout to exceed tolerance (>0.1 mm), preventing the sensor from detecting a stable signal.
  • 4Signal tone ring contaminated or damaged: Brake dust, metal filings, or muddy water adhering to the tone ring surface; broken or deformed tone ring teeth (common after accident repairs or frequent water wading), causing irregular magnetic flux changes.
  • 5Internal fault in the ABS pump assembly: Damage to the ABS control unit's internal right front wheel speed signal processing circuit, a burnt sampling resistor, or a poor ground connection causes a false sensor circuit fault diagnosis.
What To Do
  • 1
    Pre-inspection and fault confirmation: Connect the VDS or OEM diagnostic tool to read the complete fault codes. Confirm if C003504 is an Active or History fault. Review the freeze frame data and record parameters such as vehicle speed and voltage when the fault occurred. Clear the fault codes and perform a road test to confirm fault reproduction conditions.
  • 2
    Visual and mechanical inspection: Raise the vehicle and check the right front wheel speed sensor installation. Verify the bolt torque (typically 8-12N·m). Inspect the sensor head for metal shavings, oil contamination, or physical damage. Check the signal tone ring integrity and clean its surface. Manually rock the right front wheel to check bearing clearance and verify there is no radial or axial play.
  • 3
    Electrical parameter measurement: Disconnect the sensor connector and measure the sensor resistance (magnetic inductive type: 1.0-1.5 kΩ; Hall type requires a power supply test). Measure the harness-side supply voltage (12V ± 0.5V, ignition ON) and ground wire resistance (<1 Ω). Use an oscilloscope to check the signal waveform. Verify a sine wave (magnetic inductive type) or square wave (Hall type) with normal amplitude.
  • 4
    Harness continuity and insulation check: Test continuity from the sensor connector to the ABS pump ECU connector (resistance <1Ω). Measure signal wire insulation resistance to ground and to power (>10MΩ). Inspect harness securing points at wear-prone areas, such as the right front frame rail in the engine compartment and the fender liner. Repair damaged sections and install corrugated conduit.
  • 5
    Component replacement and verification: If measurements confirm a faulty sensor, replace the right front wheel speed sensor with an OEM part (distinguish between magnetic inductive and Hall types; E5 typically uses the Hall type). If the bearing has excessive play, replace the wheel hub bearing assembly. After repair, clear the fault code, calibrate the wheel speed sensor (if required by the system), perform a 5-10 km/h low-speed driving test to confirm four-wheel speed signal synchronization, and perform a final ABS/ESP dynamic road test.
Real-World Cases
BYD DTC AI Analysis

E5: Sensor contamination and connector oxidation caused abnormal signal

✓
A 2018 BYD E5 with 80,000 km had constant ABS and ESP warning lights on the instrument panel. The scan tool read fault code C003504. Technicians removed the right front wheel speed sensor and found the magnetic head coated in iron filings and brake dust. The sensor plug pins showed white oxidation. They cleaned the sensor head and tone ring with carburetor cleaner, sanded the plug pins with fine sandpaper to remove the oxidation, applied conductive grease, and reinstalled. They cleared the fault codes and road tested; the wheel speed signal returned to normal and the warning lights went out. This fault is relatively common in vehicles driven through water or used long-term in humid conditions.
Original source ↗
BYD DTC AI Analysis

Song Pro: Excessive play in right front wheel bearing causing intermittent fault

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2019 BYD Song Pro DM, 120,000 km. Dashboard intermittently displayed "Check ESP System". Scan tool showed C003504 as an intermittent fault. Data stream showed right front wheel speed signal occasionally dropping to zero or deviating more than 5 km/h from other wheels. Raised the vehicle and found obvious radial play in the right front wheel bearing (approximately 2 mm), causing the reluctor ring to oscillate radially relative to the sensor during rotation. Replaced the right front hub bearing assembly and readjusted the sensor installation clearance to 0.8 mm. Fault eliminated. Replacing the sensor alone won't fix this type of mechanical wear.
BYD DTC AI Analysis

Wiring harness chafing causes intermittent open circuit in E5 EV

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A BYD E5 taxi with 150,000 km on the clock failed to enter READY mode, the instrument cluster displaying a brake system fault. DTC C003504 (current fault) present. Inspection found the RH front wheel speed sensor wiring harness had come loose from its retaining clip at the RH front longitudinal member in the engine bay. The harness had rubbed against the body panel, wearing through the insulation and breaking the copper cores of both internal wires, causing an intermittent open circuit. We stripped back the harness, re-soldered the broken conductors, insulated them with heat-shrink tubing, properly re-routed and secured the harness, and fitted protective corrugated conduit. The vehicle returned to normal after repair, with regenerative braking function restored.
Original source ↗
BYD DTC AI Analysis

Qin EV sensor body aging failure

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2018 BYD Qin EV450, 60,000 km. ABS warning light constantly on. Scanned with a diagnostic tool and found DTC C003504—active static fault. Tested the right front wheel speed sensor: power supply normal at 12.4 V, but no pulse signal at the output. Removed the sensor and measured resistance; open circuit (infinite). Internal coil break confirmed. Replaced with an OEM right front wheel speed sensor (part number: 3630420-XXX). Executed the 'sensor calibration' procedure with the scan tool, cleared the codes and road tested. All four wheel speed signals consistent; ABS function restored.
BYD DTC AI Analysis

Tone ring deformed after accident repair, causing signal distortion

✓
A BYD e5 that had undergone right-front collision repairs at a dealership traveled approximately 1,000 km before the ESC warning light illuminated, logging code C003504. Inspection found the replacement right-front steering knuckle assembly (including the signal reluctor ring) installed during the accident repair was slightly deformed, causing reluctor ring radial runout of 0.3 mm (specification <0.1 mm). The sensor detected a signal, but waveform amplitude was unstable, so the ABS pump flagged a circuit fault. Replaced the steering knuckle and hub bearing assembly with a qualified unit, calibrated reluctor ring radial runout to within 0.05 mm using a dial gauge, and cleared the fault.
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.