How to diagnose an ABS problem

Check the fuses and relay first ===check wiring and connections to the abs sensors lot of times debris damages or disconnects the line the wiring is behind wheel to frame also check hub if hub is going abs usually pops trouble light the hub and abs are incorporated together the abs wire goes to a ring style which is fitted around hub and are mounted in spindle

You need to find out what code is stored in the ABS control module, if the light is on there is a DTC an the system is disabled ! Don't know if auto part stores can pull ABS codes or not , You'll have to check it out . Personally I say take it to a ASE certified repair shop if you don't know anything about anti lock brakes !
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Electronic Brake Control Module (EBCM) -- The EBCM controls the system functions and detects failures.

The EBCM contains the following components:

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System Relays -- The inlet and outlet solenoid relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves, the pump motor relay is energized and supplies battery positive voltage to the pump motor when ABS is activated.

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Brake Pressure Modulator Valve (BPMV) -- The BPMV contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4 circuit configuration with a diagonal split. The BPMV directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.

This system can store 10-12 DTC's for something simple as wheel speed sensors to wiring problems to a malfunction of the EBCM . Some of these problems you would need a professional type scan tool ! The antilock brake system on your vehicle is the
BOSCH 8.0 antilock braking system
The vehicle is equipped with the following braking systems:
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Antilock Brake System (ABS)

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Dynamic Rear Proportioning (DRP)

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Traction Control System (TCS) (w/NW7)

The following components are involved in the operation of the above systems:
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Electronic Brake Control Module (EBCM) -- The EBCM controls the system functions and detects failures.

The EBCM contains the following components:

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System Relays -- The inlet and outlet solenoid relay is energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves, the pump motor relay is energized and supplies battery positive voltage to the pump motor when ABS is activated.

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Brake Pressure Modulator Valve (BPMV) -- The BPMV contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4 circuit configuration with a diagonal split. The BPMV directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other.

Important: There is a rubber isolator located under the BPMV and on the mounting studs. The rubber isolators protect the BPMV and the EBCM from vehicle vibrations.

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The BPMV contains the following components:

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Pump Motor

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Inlet Valves (one per wheel)

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Outlet Valves (one per wheel)

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Wheel Speed Sensors (WSS) -- As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses this alternating current signal to calculate wheel speed. The wheel speed sensors are replaceable only as part of the wheel hub and bearing assemblies.

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Traction Control Switch (w/NW7) -- The TCS is manually disabled or enabled using the traction control switch.

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Stop Lamp Switch - The EBCM uses the stop lamp switch as an indication that the brake pedal is applied