For 1990-2009 cars

Before using this section, 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 contained in this section.

If you need a review of basic electrical troubleshooting knowledge, Refer to General Electrical Diagnosis in Wiring Systems. 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). Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.

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

• | You should understand what happens in a voltage circuit with an open or shorted wire. Refer to Measuring Voltage in Wiring Systems.

• | You should understand what happens in a circuit with a short to ground. Refer to Testing for Short to Ground in Wiring Systems.

### Use of Circuit Testing Tools

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.

• | You should be able to use and understand how to work with a scan tool. Refer to scan tool manual for complete information or Scan Tool Diagnostics in this ABS section for more information.

• | You should be familiar with the Digital Multimeter (DMM) J 39200 , and be familiar with the meter controls and how to use them correctly. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.

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

• | You should be able to test for electrical intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

• | You should know how to use jumper wires to bypass components for testing circuits. Refer to Using Fused Jumper Wires in Wiring Systems.