For 1990-2009 cars

It is important that you have a basic knowledge of the following items. Without this basic knowledge, it will be difficult to use the diagnostic procedures properly.

If you need a review of basic electrical troubleshooting knowledge, Refer to General Electrical Diagnosis in Wiring Systems. This contains helpful information including the basic use of circuit testing tools. Additionally, electrical/electronic courses are offered through General Motors Service Training.

### Basic Electrical Circuits

• | You should understand the basic theory of electricity and know the meaning of voltage, current (amperes) and resistance (ohms).

• | You should understand what happens in a circuit with an open or shorted wire.

• | You should be able to read and understand a wiring diagram.

### Use of Circuit Testing Tools

• | You should be familiar with the Digital Multimeter (DMM) and be familiar with the meter controls and how to use them correctly.

• | You should be able to measure voltage, resistance and current.

• | You should know how to use jumper wires to bypass components for testing circuits.

| Important: When measuring the resistance to ground of circuit or component, make sure to use a solid, unpainted chassis ground or the negative battery terminal.