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

Do Not perform this check if a driveability concern is not present.

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

If the problem is intermittent, refer to Intermittent Conditions .

Important: Checking for applicable service bulletins is recommended.

The number(s) below refer to step numbers on the diagnostic table:

1. Do not perform the Powertrain OBD System Check unless one of the concerns noted is present. Failure to follow this procedure could lead to misdiagnosis of the system.

   If the only symptom is an inoperative MIL and DTC P0650 is not set, check for an internal instrument cluster problem. Refer to Diagnostic System Check - Instrument Cluster in Instrument Panel, Cluster, and Console.

2. The diagnostic tables in this section are designed for use with a scan tool. If the scan tool is inoperative, this condition must be corrected before beginning any other diagnostic procedures. Do Not clear the DTCs unless you are instructed to do so by a diagnostic procedure.

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

1.	PCM failure DTCs (P0601, P0602).

2.	System Voltage DTCs.

3.	Component level DTCs (the Sensors, the Solenoids, the Relays etc.). Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC.

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

5.	Transmission DTCs. The transmission DTCs are not located in this section. Refer to Diagnostic Trouble Code Identification in Transmission/Transaxle.

When there is a known exception, a DTC table may direct the technician to diagnose other DTCs first.

6. Capturing the stored Information will preserve the data that will be lost when you are instructed to clear the DTCs at the end of a diagnostic table, or if a PCM disconnect or replacement occurs during a diagnostic procedure. Even if additional DTCs are inadvertently set while performing diagnostics or repairs, the original data is stored in the scan tool for future use. The captured Information should be reviewed at the end of the diagnostic table in order to catch the next DTC in the event that multiple DTCs were stored. Follow the order of priority as listed above.

7. Normal MIL operation is as follows:

   With the key on and the engine off the MIL should be on.

   With the engine running and no DTCs requesting the MIL (MIL Request) the MIL should be off.

   The scan tool should be able to command the MIL on and off.

8. Compare the actual control system data with the values in the Engine Scan Tool Data List in order to determine if any parameter is not within limits. Keep in mind that a base engine problem (for example, advanced cam timing) may substantially alter the sensor values. If the actual data does not correspond with the values in the Engine Scan Tool Data List , but the corresponding DTC is not set, there are specific conditions that have to be met before some diagnostics will run. This information is in the supporting text for the DTC table. If a system fault is suspected (the EVAP operation, the HO2S operation, etc.) refer to the DTCs that apply to that system. The DTC tables are not designed to be used unless a DTC is set, however, many tables begin with a functional test of the related component. This information can be a useful aid in diagnosis.