Important: Do not perform this check if no driveability condition exists, unless you are directed from another procedure.

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

Important: For automatic transmission DTCs, refer to Diagnostic Trouble Code Identification in Automatic Transmission-4L60-E 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 .

Important: This vehicle is equipped with a Powertrain Control Module (PCM) utilizing an Electrically Erasable Programmable Read Only Memory (EEPROM). Program the new PCM when diagnostics call for replacement of the PCM. When the PCM is replaced the following must be performed:

1. The PCM must be programed. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement .
2. The PCM Password Learn Procedure. Refer to DTC P1631 Theft Deterrent Start Enable Signal Not Correct .
3. The PCM Idle Learn Procedure. Refer to Idle Learn .

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.

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 mini relay for proper operation. The following components are powered by the IGN mini relay:

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.

3. This check will determine if any other modules on the Class 2 circuit can communicate. If no communication occurs with any other module, the class 2 circuit is shorted to ground, is open, is shorted to a voltage, or one of the modules is causing no communications. Further diagnosis is required. Refer to Body and Accessories.

5. This step checks for DTCs associated with the Vehicle Theft Deterrent system which will prevent the engine from starting.

6. This condition may indicate a problem 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.)

For Automatic Transmission DTCs, Refer to Transmission/Transaxle/Automatic Transmission.

8. 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 problem (i.e. advanced cam timing) may substantially alter sensor values. If the actual data does not correspond with the values in the Engine Scan Tool Data List, refer to the appropriate system/component diagnostic aids or test descriptions.