Diagnostic Starting Point - Antilock Brake System

VISUAL INSPECTION
A careful visual and physical inspection must be part of every diagnostic routine. This can often identify a problem without further steps. Inspect all engine compartment and wheel speed sensor wiring for:
^ Proper connection
^ Burned, chafed or pinched wires
^ Contact with sharp edges or exhaust manifolds
^ Signs of tampering

Inspect vehicle tires for:
^ Proper size
^ Consistent inflation pressure
^ Tread condition
The visual inspection is very important. It must be done carefully.