Refer to
Power, Ground, MIL, and DLC
Circuit Description
The Powertrain OBD system check is an organized approach to identifying a problem created by an electronic engine control system malfunction. The Powertrain OBD system check must be the starting point for any driveability complaint diagnosis. The Powertrain OBD system check directs the service technician to the next logical step in diagnosing a complaint. Do not perform this check if no driveability complaint exists. Understanding the table and using it correctly will reduce diagnostic time and prevent the replacement of good parts.
Important: This vehicle is equipped with a Powertrain Control Module (PCM) utilizing an Electrically Erasable Programmable Read Only Memory (EEPROM). When diagnostics call for replacement of the PCM, the new PCM must be programmed.
Refer to Powertrain Control Module Replacemment.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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The MIL should be ON steady with the key ON/engine OFF. If not, the No Malfunction Indicator Lamp should be used to isolate the malfunction.
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This test ensures that the PCM is capable transmitting Class 2 serial data to the DLC and that the Class 2 data circuit is not open or shorted. If a DLC problem exists, the Data Link Connector Diagnosis should be used to diagnose the condition.
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If the engine will not start, the Engine Cranks but Does Not Run should be used to diagnose the condition.
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The scan tool may display DTC(s) which are diagnosed in 4T60-E Automatic Transaxle Diagnosis, Section 7. Refer to the Powertrain Diagnostic Trouble Codes table for a complete list of DTC(s) supported by this vehicle application.
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A scan tool parameter which is not within the typical range may help to isolate the area which is causing the problem.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Is the MIL ON? | -- | Go to No Malfunction Indicator Lamp | |
2 |
Does the scan tool display PCM data? | -- | Go to Data Link Connector Diagnosis | |
3 | Attempt to start the engine. Did the engine start and continue to run? | -- | Go to Engine Cranks but Does Not Run | |
4 | Display DTC Info Last Tst Fail. If any DTCs are stored as last test failed, save the freeze frame and fail record information using the Capture Info feature on the scan tool. Are any DTCs indicated as last test failed? | -- | Diagnose the applicable DTC(s). Refer to Powertrain Diagnostic Trouble Codes | |
5 | Display DTC Fail Records with the scan tool. If any DTC Fail Records are stored, save the freeze frame and fail record information using the Capture Info feature on the scan tool. Are any Fail Records stored? | -- | Go to applicable DTC table | |
6 | Compare PCM data values displayed on the scan tool to the typical engine scan data values. Are the displayed values normal or close to the typical values? | -- | System OK | Refer to indicated Component System Checks |
