* Low brake fluid: This is the most common and easiest to check. Simply inspect your brake fluid reservoir. If it's low, you need to add fluid and investigate the source of the leak.
* Faulty wheel speed sensor: These sensors detect wheel rotation and are crucial for ABS function. A malfunctioning sensor can trigger the light. They can be damaged, corroded, or have wiring problems.
* Faulty ABS module: The ABS module is the computer controlling the system. A failure in the module itself requires professional diagnosis and likely replacement.
* Faulty ABS pump: The pump is responsible for pressurizing the system. If it fails, the ABS light will come on. This is also a complex repair typically requiring professional attention.
* Wiring issues: Corrosion, broken wires, or poor connections in the ABS system's wiring can cause problems.
* Low battery voltage: A weak battery can sometimes cause the ABS light to illuminate.
To diagnose the problem, you'll likely need:
* A visual inspection: Check brake fluid level, and look for any obvious damage to wiring or sensors.
* An OBD-II scanner (possibly not for a 1991): While 1991 models may not fully support OBD-II, a scanner *might* be able to retrieve some diagnostic trouble codes (DTCs) related to the ABS system. However, more specialized tools are often needed.
* A professional mechanic: For a car this old, taking it to a mechanic specializing in older vehicles is often the best and most cost-effective solution. They have the tools and expertise to diagnose and fix the problem accurately.
Don't drive with a malfunctioning ABS system. While the brakes will still work, the anti-lock braking system won't be active, potentially leading to loss of control during braking in adverse conditions.
