* ABS Module is Central: The ABS module is often the common denominator. It controls not only the anti-lock braking system but also frequently interacts with, or shares components with, the traction control system. A malfunction in the ABS module can trigger both the ABS and Trac Off lights.
* SES Light Trigger: The computer (PCM or ECM) detects a malfunction in the ABS system, and because it's a significant failure impacting safety and drivability, the SES light also activates as a secondary warning.
Possible Causes:
* Faulty ABS Module: This is the most likely culprit. The module itself could be failing internally, or it might have a power or ground issue.
* Wheel Speed Sensor: A faulty wheel speed sensor (one or more) can prevent the ABS system from functioning correctly and will trigger the lights. These sensors are relatively inexpensive to replace, but diagnosis is key to pinpoint the faulty sensor.
* Low Brake Fluid: While less likely to trigger *all three* lights simultaneously, critically low brake fluid can affect ABS operation and cause these warnings. Check your brake fluid level immediately.
* Wiring Issues: Damaged, corroded, or loose wiring within the ABS system can disrupt communication between the components and trigger the warning lights.
* Other less common issues: Issues with the brake pressure sensor, ABS pump motor, or even the battery voltage can contribute.
What You Should Do:
1. Check Brake Fluid: This is the quickest and easiest check. Low fluid is a serious problem that needs immediate attention.
2. Obtain a Diagnostic Trouble Code (DTC): You'll need an OBD-II scanner to retrieve the specific trouble codes stored by the car's computer. This provides valuable clues about the root cause. Auto parts stores often offer free code reading services.
3. Professional Diagnosis: Once you have the DTCs, it's best to take your Alero to a qualified mechanic specializing in automotive electronics. They have the tools and expertise to diagnose and repair the issue effectively and safely. Trying to fix an ABS problem yourself can be risky if not properly understood.
Ignoring these lights is unsafe. The ABS and traction control systems are crucial for safe braking and handling, especially in adverse conditions. Have your vehicle checked immediately.
