Important: Do not perform this diagnostic if no driveability concern exists. A driveability condition includes all PCM controlled systems and components.

The Powertrain OBD System Check is an organized approach to identifying a concern created by an electronic engine control system malfunction. The Powertrain OBD System Check is the starting point for any driveability concern diagnosis. The Powertrain OBD System Check directs the service technician to the next logical step in diagnosing a concern. Understanding and using the table correctly will reduce the diagnostic time and prevent the replacement of good parts.

Important: For automatic transmission DTCs, refer to Diagnostic Trouble Code (DTC) Type Definitions in Automatic Transmission-4L60E for diagnosis procedures. The DTCs associated with the automatic transmission are:

Important: For Domestic and Export DTC Types, refer to Diagnostic Trouble Code (DTC) List/Type .

Important: 

This vehicle has a column lock system. This system is necessary because of the location of the ignition lock cylinder. The BCM controls a motor mounted on the steering column. The purpose of the motor is to unlock the steering wheel. The PCM will disable the fuel if the BCM is unable to determine if either the column is unlocked or vehicle speed is present. Refer to Diagnostic System Check - Body Control System in Body Control Systems for more information on the column lock system.

Important: If an intermittent condition exists, inspect the PCM wiring harnesses for improper installation of electrical components. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. Ensure that no aftermarket equipment is connected to the Class 2 circuit. A cellular phone signal communication may cause an intermittent condition.

If multiple DTCs are set, inspect the IGN relay for proper operation. Refer to Ignition Relay Diagnosis .

The numbers below refer to the step numbers on the diagnostic table.

1. Use a properly functioning scan tool with the diagnostic tables in this section. DO NOT use the Clear Info function unless instructed by a diagnostic procedure.

2. This step verifies that the scan tool communicates with the PCM.

5. This step tests for DTCs associated with the Vehicle Theft Deterrent system which prevents the engine from starting.

6. This step inspects for a condition that may indicate a concern with the Column Lock system.

7. If multiple DTCs are stored, diagnose in the following order of priority:

1.	PCM/TAC failure DTCs (P0601, P0602, P0604, P0606, P1517, P1518)

2.	System Voltage DTCs

3.	Component level DTCs (Sensors, Solenoids, Relays , etc.)

Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC.

4.	System level DTCs (Misfire, Fuel Trim, etc.)

9. Capturing the stored information preserves data that the PCM loses when you are instructed to use the clear information function, or if you disconnect the PCM, or replace the PCM for a diagnostic procedure. The scan tool stores the data in the scan tools memory. Review the Captured Information at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored.

   It is beneficial to review the Freeze Frame data and/or Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information and the other operating conditions when the DTC set may help you diagnose an intermittent condition.

10. This step is for states that have an Inspection/Maintenance (Emission Testing) program. The testing facility found one or more I/M status flags not set.

11. Compare actual control system data with the values in the Engine Scan Tool Data List to determine if any parameter is not within limits. Keep in mind that a base engine condition (i.e., advanced cam timing) may substantially alter sensor values.