Circuit Description
The Powertrain On Board Diagnostic (OBD) System Check is an organized approach to identify a condition created by an automatic transmission. The Powertrain OBD System Check is the diagnostic starting point for an automatic transmission complaint. The Powertrain OBD System Check directs you to the next logical step for diagnosing a transmission concern. Perform this check only if there is a driveability complaint 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 DTC(s) will erase all Freeze Frame and Failure Records stored in PCM
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
in
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: |
| - | The PCM 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.
-
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 PCM 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 | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Important:
Does the Scan Tool turn ON? | -- | Go to Scan Tool Does Not Power Up in Data Link Communications | ||||||
Is the MIL ON? | -- | Go to Malfunction Indicator Lamp (MIL) Inoperative in Engine Controls | ||||||
Attempt to establish communication with the PCM controller module. Does the Scan Tool communicate with the PCM control module? | -- | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | ||||||
Use the Scan Tool Capture Info function in order to save or capture (Store Info) any DTC information. Important: Diagnostic Trouble Codes (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. Are there any DTCs present? | -- |
