ABS and Traction Control Lights ON in 2020 Envision

ClearTheCode admin answer:

When both the ABS (Anti-lock Braking System) and Traction Control System (TCS) lights illuminate simultaneously on your 2020 Buick Envision Essence, it indicates that a fault has been detected in one of the shared components or systems that both rely on. While your regular braking might feel normal, the ABS and TCS functions are likely disabled, which can affect safety in emergency braking or slippery conditions.

Here are the most common causes:

1. Wheel Speed Sensor Failure: This is by far the most frequent cause. Each wheel has a sensor that monitors its rotational speed. If a sensor fails (due to dirt, damage, or electrical fault), the ABS and TCS modules lose crucial data, triggering both lights. Common OBD-II codes related to this include:
   • C0035 (Left Front Wheel Speed Sensor Circuit)
   • C0040 (Right Front Wheel Speed Sensor Circuit)
   • C0045 (Left Rear Wheel Speed Sensor Circuit)
   • C0050 (Right Rear Wheel Speed Sensor Circuit)
2. Damaged Wiring or Connector: The wiring harness or connectors leading to a wheel speed sensor can become corroded, frayed, or damaged, interrupting the signal.
3. ABS Module Failure: Less common, but the ABS control module itself can fail. This is a more expensive repair and often presents with multiple codes or intermittent issues.
4. Low Brake Fluid Level: While less likely to trigger both lights without a brake warning light, extremely low fluid can sometimes confuse the system.
5. Faulty Tone Ring: The tone ring (or reluctor ring) is a toothed wheel that the wheel speed sensor reads. If it's damaged or corroded, the sensor won't get an accurate reading.

When to See a Shop:

• Promptly: While your regular brakes may work, the safety features of ABS and TCS are disabled. This means your wheels could lock up under hard braking, and you won't have traction assistance on slippery surfaces. It's advisable to have it checked as soon as possible.
• Professional Diagnosis: A mechanic will use a specialized scan tool to read the diagnostic trouble codes (DTCs) stored in the ABS module. These codes will pinpoint the specific area of the fault, allowing for accurate diagnosis and repair. Do not attempt to clear the codes without addressing the underlying issue, as the lights will simply return.