2021 NX 300h ABS and Traction Control Lights On

ClearTheCode admin answer:

It's concerning when both the ABS and Traction Control lights illuminate on your 2021 Lexus NX 300h, even if the car seems to drive normally. These lights indicate that critical safety systems designed to prevent wheel lock-up during braking (ABS) and maintain traction during acceleration or cornering (Traction Control) are currently disabled or experiencing a fault. While the brakes might feel normal, the advanced features of these systems are not active.

Here are the most common causes for both lights to come on simultaneously:

1. Wheel Speed Sensor Failure:

   • Cause: This is the most frequent culprit. Each wheel has a sensor that monitors its rotational speed. If one sensor fails, sends erratic signals, or its wiring is damaged, the ABS and Traction Control systems lose crucial data, causing both lights to illuminate.
   • Action: A diagnostic scan tool (not a basic OBD-II scanner, but one capable of reading ABS/VSC codes) will typically show a specific code for the faulty wheel speed sensor (e.g., C0031 for front left, C0034 for front right, etc.).

2. ABS Module/Hydraulic Control Unit (HCU) Issues:

   • Cause: The ABS module is the brain of the system, and the HCU controls the brake fluid pressure to each wheel. A fault within this complex unit, either electrical or mechanical, can disable both systems.
   • Action: This is a more serious and potentially costly repair. Specific codes (e.g., C1241 for low voltage, C1256 for accumulator pressure) would point to this. Diagnosis requires advanced tools.

3. Brake Light Switch:

   • Cause: A faulty brake light switch can sometimes cause these lights to come on, as it provides input to the ABS/VSC system. If the system doesn't know when the brakes are being applied, it can trigger faults.
   • Action: Check if your brake lights are functioning correctly. This is a relatively inexpensive part to replace if found faulty.

4. Low Brake Fluid Level:

   • Cause: While less common to trigger both lights simultaneously without other brake warnings, extremely low brake fluid can sometimes affect system performance.
   • Action: Check your brake fluid reservoir level. Ensure it's within the MIN/MAX marks.

5. Steering Angle Sensor:

   • Cause: The steering angle sensor provides input to the Traction Control and Stability Control systems about the steering wheel's position. A fault here can confuse the system.
   • Action: A specific diagnostic code (e.g., C1290) would indicate an issue with this sensor.

When to See a Shop:

Since both the ABS and Traction Control systems are safety-critical, it's highly recommended to have your 2021 Lexus NX 300h diagnosed by a professional technician as soon as possible. A standard OBD-II scanner will likely not read the specific ABS/VSC codes. A Lexus dealership or a shop with advanced diagnostic equipment can retrieve these codes, accurately pinpoint the problem, and ensure your safety systems are fully functional.