Diagnostic System Check - Automatic Transmission

Diagnostic System Check - Automatic Transmission

Circuit Description

The Diagnostic System Check - Automatic Transmission is an organized approach to identifying a condition created by an automatic transmission. The Diagnostic System Check is the diagnostic starting point for an automatic transmission concern. The Diagnostic System Check directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveablity 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 diagnostic trouble code (DTC) unless directed by a diagnostic procedure. Clearing the DTC will erase all Freeze Frame and Failure Records stored in engine control module (ECM) memory

* Poor engine performance can sometimes be diagnosed as a transmission, always perform Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle.


* 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.

- The ECM 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.
1. This step determines if the scan tool is receiving power through the DLC connector.
2. This step determines if the ECM is transmitting serial data to the DLC and that the serial data circuit is not open or shorted.
3. This step determines if an ECM DTC is current or stored in history.
4. This step determines if the TCM is transmitting serial data to the DLC and that the serial data circuit is not open or shorted.
5. This step determines if an ECM DTC is current or stored in history.