2023 MX-5 Miata ABS and TCS Lights On - Wheel Speed Sensor?

ClearTheCode admin answer:

When both the ABS and TCS lights illuminate, it strongly suggests a problem within the anti-lock braking system, as the TCS relies on the same wheel speed sensor data. A faulty wheel speed sensor is indeed the most common cause, even on newer vehicles.

1. Scan for ABS/TCS Codes: A standard OBD-II scanner may only read engine codes (P-codes). You'll need a scanner capable of accessing the ABS module to read specific trouble codes (C-codes). These codes will often directly tell you which wheel speed sensor (e.g., C0031 for Front Left Wheel Speed Sensor) or circuit is faulty.
2. Visual Inspection of Sensors and Wiring: Once you have a potential culprit, visually inspect the wheel speed sensor and its wiring harness at that wheel. Look for:
   • Physical Damage: The sensor itself can be damaged by road debris.
   • Corrosion: Especially where the sensor plugs into the harness.
   • Loose Connections: Ensure the connector is fully seated.
   • Damaged Wiring: Look for frayed, cut, or pinched wires, especially near the wheel well where they are exposed to movement and elements.
3. Check Tone Ring: The wheel speed sensor reads a 'tone ring' (also called an ABS ring or reluctor ring) on the axle or hub. Inspect this ring for damage, cracks, or excessive dirt/debris that could interfere with the sensor's reading.
4. Hub Bearing Play: In some cases, excessive play in a wheel bearing can cause the tone ring to wobble, leading to inconsistent sensor readings. While less likely on a 2023 model, it's worth noting.

When to see a shop: If you can't access ABS-specific codes or if a visual inspection doesn't reveal an obvious issue, it's best to take your Miata to a professional. A technician can use a more advanced diagnostic scanner to read live data from each wheel speed sensor while driving, pinpointing which sensor is reporting an incorrect or no signal. They can also perform continuity tests on the wiring and thoroughly inspect components that might be harder to access, ensuring a correct diagnosis and repair.