Important: Do not perform the Diagnostic System Check - Automatic Transmission unless one of the concerns noted is present. Failure to follow this procedure could lead to misdiagnosis of the system.

The Diagnostic System Check - Automatic Transmission is an organized approach to identifying a condition identified by the transmission electronic control system.

When an emission related DTC (type B) sets because of an automatic transmission fault, the TCM requests the Engine Control Module (ECM) to activate the instrument cluster Check Powertrain Malfunction Indicator Lamp (MIL). The ECM may also independently activate the MIL. Although either module may cause the MIL to activate, Tech 2 can display DTCs from only one module at a time. However the 'Clear DTC Info' command clears DTC data from both modules. If the DTC failure records are not recorded from both modules before the DTC data is cleared, important diagnostic information will be erased.

Your training and experience as a Technician may cause you to focus on either the TCM or the ECM, instead of both modules at the same time. To ensure that both modules are properly diagnosed, separate system checks are included. The process detailed in the Diagnostic System Check - Vehicle identifies whether ECM related DTCs are recorded. If no ECM DTCs are present, you will then be directed to this, Diagnostic System Check - Automatic Transmission.

The ECM diagnostics do not require automatic transmission data to run. Correct use of the tables will reduce diagnostic time and prevent the replacement of good parts.

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

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

1. Do not perform the Diagnostic System Check - Automatic Transmission unless the Diagnostic System Check - Vehicle, refer to Diagnostic System Check - Vehicle , is completed first. Failure to follow this procedure could lead to misdiagnosis of the system.
2. Checks that Tech 2 powers up and that communication can be established with the Transmission Control Module (TCM).
3. Check for any applicable Service Techlines before proceeding with the diagnosis.
4. If multiple automatic transmission DTCs are stored, diagnose the DTCs in numerical order, starting with the lowest DTC number. When there is a known exception, a DTC table however, may direct you to diagnose a different DTC first.
5. Compare the actual control system data with the values in the Transmission Tech 2 Data List in this Section, to determine if any parameter is not within limits. A base engine condition, such as advanced cam timing, may substantially alter the sensor values. If the actual data does not correspond with the values in the Tech 2 Transmission Data List, but the corresponding DTC is not set, this indicates that some specific conditions have not been met before some diagnostics will run. This information is in the supporting text for the DTC table. If you suspect a system fault, such as Shift Solenoid operation, TCC operation, 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.