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 transmission control module (TCM) is transmitting serial data to the DLC and that the serial data circuit is not open or shorted.
3: This step determines if an TCM DTC is current or stored in history.
4: This step determines if the ECM 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.

Diagnostic System Check - Automatic Transmission

Step	Action	Yes	No
1	Install a scan tool. IMPORTANT: Check for applicable service bulletins before proceeding with this test. Perform this test only if there is a driveability complaint or if you have been directed to this table from another section in the service information. Do not turn ignition OFF when performing this diagnostic procedure. Do not clear the DTCs unless instructed by this diagnostic procedure. Turn ON the ignition, with the engine OFF. Does the scan tool power up?	Go to Step 2	Go to Scan Tool Does Not Power Up
2	Attempt to establish communication with the transmission control module (TCM). Does the scan tool communicate with the TCM?	Go to Step 3	Go to Scan Tool Does Not Communicate with CAN Device
3	Select the TCM DTCs function on the scan tool. Does the scan tool display any TCM DTCs?	Go to Symptoms - Automatic Transmission	Go to Step 4
4	Attempt to establish communication with the engine control module (ECM). Does the scan tool communicate with the ECM?	Go to Step 5	Go to Scan Tool Does Not Communicate with CAN Device
5	Select the ECM DTCs function on the scan tool. Does the scan tool display any ECM DTCs?	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Symptoms - Automatic Transmission