Visual Inspection

VISUAL/PHYSICAL UNDERHOOD INSPECTION
A careful visual and physical inspection must be performed as part of any diagnostic procedure or in finding the cause of a failure. This can often lead to fixing a problem without further steps. Inspect all vacuum hoses for correct routing, pinches, cuts, or disconnects. Inspect all the wires in the engine compartment and to the wheel speed sensors for proper connections, burned or chafed spots, pinched wires, or contact with sharp edges or hot exhaust manifolds. This visual/physical inspection is very important. It must be done carefully and thoroughly.

KNOWLEDGE AND TOOLS REQUIRED
A general understanding of basic electrical circuits and circuit testing tools is required. One should be familiar with wiring diagrams, the meaning of voltage, ohms, amps, the basic theories of electricity, and understand what happens in an open or shorted wire.

To perform system diagnosis, the use of a diagnostic Scan tool is required. A tachometer, test lamp, ohmmeter, digital voltmeter with 10 megohms impedance, vacuum gauge, and jumper wires are also required. Please become acquainted with the tools and their use before attempting to diagnose a vehicle.

DIAGNOSTIC INFORMATION
The diagnostic trouble tree charts and functional checks are designed to locate a faulty circuit or component through logic based on the process of elimination. The charts are prepared with the requirement that the vehicle functioned correctly at the time of assembly and that there are no multiple failures. Trouble tree charts are designed to be used only when a code is present.

The ABS control module performs a continual self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures. The language for communicating the source of a malfunction is a system of diagnostic trouble codes. The codes are two digit numbers that can range from 11 to 99. When a malfunction is detected by the ABS control module, a code is set and the ABS telltale lamp is illuminated.