For 1990-2009 cars

Before you begin any diagnostic procedure, always review the system Description and Operation. Reviewing the Description and Operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the Description and Operation information will also help you determine if the condition described by the customer is normal operation.

After reviewing the system description and operation, always begin the system diagnosis Diagnostic System Check - Vehicle with Vehicle with Vehicle DTC information.

The Diagnostic System Check will provide the following information:

• | The identification of the control modules which command the system.

• | The ability of the control modules to communicate through the serial data circuit.

• | The identification of any stored DTCs and their status.

The use Diagnostic System Check- Vehicle may identify the correct procedure for diagnosing the system and where the procedure is located.