Here's a breakdown of possible causes:
* ABS Module Failure: This is a common culprit. The Anti-lock Braking System (ABS) module itself could be malfunctioning, sending incorrect signals to the ECM and triggering both warning lights. This might involve internal circuitry, sensors, or the module's power supply.
* Wheel Speed Sensor Issues: These sensors tell the ABS module how fast each wheel is rotating. A faulty sensor (or multiple faulty sensors) can cause the ABS light to come on and also trigger a diagnostic trouble code (DTC) that illuminates the check engine light. Worn wheel bearings can also damage these sensors.
* Low Brake Fluid: While unlikely to directly illuminate the check engine light, extremely low brake fluid can impact the ABS system's functionality and cause both lights to illuminate. Check your brake fluid level immediately.
* Faulty Brake System Component: Problems with other parts of the braking system, like a leaking brake line or a faulty brake pressure sensor, can also lead to issues with the ABS system and trigger both lights.
* Wiring Problems: Damaged, corroded, or loose wiring within the ABS system or its connection to the ECM can lead to incorrect signals and illuminate both warning lights.
* Power Supply Issue: A problem with the vehicle's electrical system, such as a failing alternator or battery, could impact the ABS module's ability to function correctly.
* ECM/PCM Failure: While less common, a fault in the engine control module (ECM) or powertrain control module (PCM) could trigger both lights due to the interconnected nature of the vehicle's systems.
What to Do:
1. Check Brake Fluid: This is the easiest and safest first step. Low fluid is a serious problem requiring immediate attention.
2. Get a Diagnostic Code Scan: The most crucial step. You need a scan tool capable of reading OBD-II diagnostic trouble codes (DTCs). This will provide specific codes that pinpoint the likely cause. Auto parts stores often offer free code reading services.
3. Don't Ignore It: Driving with malfunctioning ABS can significantly reduce your braking performance, especially in emergency situations. Ignoring the warning lights could lead to an accident.
Once you have the DTCs, you can start investigating the specific problem. Repair may involve replacing a sensor, repairing wiring, or replacing a module. It's best to have a qualified mechanic diagnose and repair the issue. Attempting repairs without proper knowledge can be dangerous and potentially costly.
