2017 XC60 T5 - ABS and Traction Control lights on, intermittent issue

ClearTheCode admin answer:

When both the ABS and Traction Control (often represented by the DSTC or ESC light on Volvos) lights illuminate simultaneously, it almost always points to an issue within the Anti-lock Braking System (ABS) or its related components. Here's a breakdown:

1. Wheel Speed Sensors: This is by far the most common culprit. Each wheel has a sensor that monitors its rotational speed. If one sensor is faulty, dirty, or has a damaged wiring harness, the ABS module receives inconsistent data, triggering both warning lights. The intermittent nature of your issue strongly suggests a sensor that's failing or has an intermittent connection.
2. ABS Reluctor Ring: These are toothed rings (sometimes integrated into the wheel bearing) that the wheel speed sensor reads. If a reluctor ring is cracked, corroded, or damaged, it can cause erratic readings.
3. ABS Module Failure: While less common than sensor issues, the ABS control module itself can fail. This is a more expensive repair. Symptoms might include a firm brake pedal or unusual braking behavior, though not always.
4. Wiring Harness Issues: Damage or corrosion in the wiring leading to the wheel speed sensors or the ABS module can cause intermittent signals and trigger the lights.
5. Brake Fluid Level: A very low brake fluid level can sometimes trigger ABS-related warnings, though usually, it's the brake system warning light that comes on first.

When to See a Shop:

• A basic OBD-II scanner typically only reads powertrain (P-codes). To diagnose ABS/Traction Control issues, you need a scanner capable of reading ABS-specific codes (C-codes). A professional shop or dealership will have this equipment.
• While braking might feel normal, the safety systems are compromised. It's crucial to get this diagnosed and repaired promptly, especially before adverse weather conditions where ABS and traction control are vital.