Check the ABS fuse
Check the ABS relay
Inspect wheel speed sensors
Clean dirty sensor tips
Inspect sensor wiring and connectors
Repair damaged wiring
Check the tone rings
Replace cracked or rusted tone rings
Check the ABS module for faults
Scan for ABS trouble codes
Clear codes after repairs
Test the brake fluid level
Top off low brake fluid
Inspect brake pads and rotors
Check the battery and charging system
Replace a weak battery
Verify tire size matches on all wheels
Replace faulty wheel speed sensors
Replace a failed ABS module
Have the ABS system professionally diagnosed