Circuit Description
The Diagnostic System Check - Automatic Transmission is an organized approach to identify a condition created by an automatic transmission. The Diagnostic System Check - Automatic Transmission is the diagnostic starting point for an automatic transmission concern. The Diagnostic System Check - Automatic Transmission directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveability concern or if you have been directed here from another service information section.
Follow the table to help reduce diagnostic time and help prevent unnecessary replacement of good parts.
Diagnostic Aids
Important:
• Do not clear the DTC unless directed by a diagnostic procedure. Clearing
the DTCs will erase all Freeze Frame and Failure Records stored in transmission control
module (TCM) memory. • Poor engine performance can sometimes be diagnosed as a transmission driveability
condition. In order to avoid mis-diagnosis of the automatic transmission, always perform
Diagnostic System Check - Engine Controls
.
| • | Use a scan tool that is known to function correctly. If necessary, test the scan tool on another vehicle. |
| • | Ensure the scan tool contains the most current file available. |
| • | The scan tool will display a loss of communication error message under the following conditions: |
| - | TCM power is interrupted |
| - | The ignition switch is turned OFF |
| - | The battery voltage level is very low |
| - | A poor connection at the diagnostic link connector (DLC) |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step determines if the scan tool is receiving power through the DLC connector.
-
The MIL should illuminate whenever the ignition is ON and the engine is not running.
-
This step determines if the TCM is transmitting Class 2 serial data to the DLC and that the Class 2 data circuit is not open or shorted.
-
This step determines if a DTC is current or stored in history.
Step | Action | Yes | No |
|---|---|---|---|
Important: Check for applicable service bulletins before proceeding with this test. Perform this test only if there is a driveability concern or if you have been directed to this table from another section in the service information. Important: Do not turn the ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure. Does the scan tool turn ON? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communication | |
Is the MIL ON? | Go to Step 3 | Go to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console | |
Attempt to establish communication with the TCM. Does the scan tool communicate with the TCM? | Go to Step 4 | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communication | |
|
Important: DTCs, engine performance, and transmission default actions can greatly affect the transmission performance. Ensure that these items are not the cause of a transmission concern. Use the scan tool Capture Info function in order to save or capture, Store Info, any DTC Information. Are there any DTCs present? |
