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2018 Forester: ABS and Traction Control Lights On, Rough Braking

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Chris P. · rep 0 · May 25, 2:15 AM · 1 replies · solved · Question

Vehicle: 2018 Subaru Forester Touring

Hey everyone, I'm having an issue with my 2018 Subaru Forester Touring. Recently, both the ABS and Traction Control lights came on simultaneously on my dashboard. When this happens, the braking feels really rough and almost grinding at low speeds, like the ABS is engaging unnecessarily. It's intermittent, sometimes it goes away after restarting the car, but it always comes back.

I'm worried about driving it like this. I've heard it could be a wheel speed sensor, but I'm not sure which one or how to diagnose it myself. Has anyone experienced this with their Forester or a similar Subaru model?

What should I be looking for? Is this something I can check at home, or do I need to get it to a shop immediately? Any advice would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:15 AM

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ClearTheCode admin answer:

This is a common issue for many vehicles, including your 2018 Subaru Forester, when the ABS and Traction Control lights illuminate together. It almost always points to a fault within the ABS system, most frequently a wheel speed sensor.

  1. Diagnosis: The first step is to get the vehicle scanned for diagnostic trouble codes (DTCs). While a standard OBD-II scanner might show engine codes, an advanced scanner is usually needed to pull ABS-specific codes (C-codes). Common codes for this issue include C0031 (Left Front Wheel Speed Sensor Circuit Malfunction), C0034 (Right Front), C0037 (Left Rear), or C0040 (Right Rear). A P0500 (Vehicle Speed Sensor Malfunction) can also sometimes trigger related issues.

  2. Causes:

    • Faulty Wheel Speed Sensor: This is the most likely culprit. The sensor might be dirty, damaged, or have a broken wire. It provides data to the ABS and Traction Control modules, and incorrect readings can cause the system to malfunction.
    • Damaged ABS Tone Ring: The tone ring (or reluctor ring) is a toothed ring that the wheel speed sensor reads. If it's cracked, corroded, or has debris, it can cause erratic readings.
    • Wiring Issues: A damaged wire or loose connection to a wheel speed sensor can also cause intermittent faults.
    • ABS Module Failure: Less common, but possible. If all sensors check out, the ABS control module itself could be faulty.

  3. When to See a Shop:

    • Immediately: Since braking performance is compromised (rough/grinding), and safety systems are affected, it's crucial to have this inspected by a qualified mechanic as soon as possible. Driving with a malfunctioning ABS system can increase stopping distances and reduce vehicle stability during emergency braking.
    • Professional Diagnosis: A professional shop has specialized diagnostic tools to pinpoint the exact sensor or component causing the issue and can perform necessary repairs or replacements. They can also inspect for any related damage to the brake system.
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