For 1990-2009 cars

Begin the system diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic System Check provides the following information:

• | The identification of the control module or modules which commands the system

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

• | The identification and status of stored diagnostic trouble codes (DTCs)

The use of the Diagnostic System Check - Vehicle identifies the correct procedure for diagnosing the system and the procedure location.

### Symptoms

When it has been determined through the Diagnostic System Check - Vehicle that no engine control module (ECM) DTCs are present, begin the Diagnostic System Check - Automatic Transmission .

The Diagnostic System Check - Automatic Transmission is an organized approach to identify a condition created by an automatic transmission. The Diagnostic System Check is the diagnostic starting point for an automatic transmission concern. The Diagnostic System Check directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveability concern or if you have been directed here from another service information section. Follow the table to help reduce diagnostic time and help prevent unnecessary replacement of good parts. If there are no transmission control module (TCM) DTCs, begin symptom diagnosis by reviewing the Transmission General Description . Reviewing the Transmission General Description information enables you to understand the operation of the system. This helps you determine if the condition described by the customer is normal or if a malfunction exists. If it is determined that a malfunction exists, identify the concern by referring to Symptoms - Automatic Transmission .