The Transmission OBD System check is an organized approach to identifying a problem created by an electronic Transmission control system malfunction. You must use the Transmission OBD system check in conjunction with the Powertrain OBD System Check when an emission related condition occurs, but you may use the Transmission OBD system check independently for non-emission related conditions. Together, they form the starting point for any driveability complaint diagnosis and direct the service technician to the next logical step in diagnosing the complaint. Understanding and using the table correctly will reduce diagnostic time and prevent the replacement of good parts.

Do not perform this check if a driveability complaint is not present.

Inspect all of the related wiring and connections including the connections at the TCM, as these may cause an intermittent malfunction. Inspect the terminals for any damage or any corrosion. Inspect the connector for any pushed out terminals.

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

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

2. The diagnostic tables in this section are, by design, for use with a scan tool. If the scan tool is inoperative, you must correct this malfunction before beginning any other diagnostic procedures. Do not clear the DTCs unless instructed by a diagnostic procedure.

6. Check for applicable service bulletins before proceeding with the diagnosis.

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

1. The ECM failure DTCs (P0601, P0602).
2. The System Voltage DTCs.
3. Component level DTCs (Sensors, Solenoids, Relays etc.). Diagnose the multiple DTCs within this category in numerical order starting with the lowest DTC number.
4. The System level DTCs (Misfire, Fuel Trim, etc.).
5. The Transmission DTCs. Refer to Diagnostic Trouble Code Identification for transmission diagnostics.

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

8. Capturing the stored Information will preserve the data that will be lost upon instruction to clear the DTCs at the end of a diagnostic table, or if a TCM disconnect or replacement occurs during a diagnostic procedure. Write down any non-emissions DTCs that are set at this time. Review the captured Information at the end of the diagnostic table in order to catch the next DTC in the event that the multiple DTCs were stored. Follow the order of priority as listed above.

9. Verify that no DTCs are set. If a DTC sets during this check, go back to Step 7.

10. Compare the actual control system data with the values in the Transmission Scan Tool Data Values in order 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 the sensor values. If the actual data does not correspond with the values in the Typical Scan Tool Data Values table, but the corresponding DTC is not set, this indicates that you have to meet specific conditions before some diagnostics will run. This information is in the supporting text for the DTC table. If you suspect a system fault (1-2 Shift Solenoid operation, TCC operation, etc.), refer to the DTCs that apply to that system. The DTC tables are not, by design, for use 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.