- Diagnostic Procedure

How To Use Powertrain Management

Powertrain Management is designed as the starting point for all powertrain diagnosis. It contains a basic description of this powertrain, detailed information on the PCM, on-board diagnostics, and selected other components as well as references to other sections for detailed information on powertrain subsystems. Before diagnosing this vehicle, you should have read and be familiar with:

^ Any training material relating to this powertrain.
^ Any bulletins released regarding this powertrain.

Once familiar with this information, you may proceed with diagnosis.

Where To Start Diagnosis

If you are reasonably certain that the problem is powertrain related, the first place to start is with the powertrain Diagnostic System Check.

While performing diagnosis, you may need to access certain components. Be sure to read the On-Vehicle Service procedures for those components before accessing them.

During diagnosis or if a wiring problem is found, you may need to refer to Diagrams. Diagrams contains complete information on this vehicle's wiring including:

1. Wiring schematics, including circuit numbers and colors.
2. Electrical component, connector, splice, and ground locations.
3. Wiring repair procedures.
4. Wiring repair parts information.

After Diagnosis Is Complete

After diagnosing a problem, in addition to repairing the discovered fault, it is a good idea to clear any DTC(s) set and verify proper operation. To clear DTC(s), refer to Clearing Diagnostic Trouble Codes under Vehicle On-Board Diagnostics. To verify a repair, you must duplicate the conditions when the customers complaint occurred or if a DTC was set, you must duplicate the Test Conditions for that DTC and see if the DTC sets. If the DTC runs and passes, chances are good that the problem is repaired.

Diagnostic Procedure Use

The diagnostic procedures used in Powertrain Management are designed to find and repair powertrain related problems. The general approach is to find the appropriate diagnosis for a problem with five basic steps described below.

1. Understand the customers complaint. It is critical that the technician understand what the customers complaint is. Failure to understand this may lead to misdiagnosis or unnecessary diagnosis. Among other things, the technician must know whether the condition is present at all times, only under certain circumstances, or truly intermittent (random). This will assist the technician in duplicating and diagnosing the problem. Another reason the technician must understand the customers complaint is so the technician may determine whether the complaint requires service or is normal vehicle operation. Trying to diagnose a complaint that is normal will waste time and may result in unnecessary service.
2. Are Diagnostics working properly? Use the powertrain on-board Diagnostic System Check. This is the starting point for the diagnostic procedure, always begin here.
3. Are DTC(s) displayed? If a DTC is identified by diagnostics, the powertrain on-board Diagnostic System Check will direct you to the appropriate diagnostic table.
4. Is the customer's complaint related to a specific powertrain subsystem? It no related DTC(s) are set, the next quickest way to locate the problem is to narrow it down to a specific powertrain subsystem. If a specific subsystem can be pinpointed as the cause, it is easier to diagnose.
5. Is the problem powertrain related? Some customer complaints may appear to be powertrain related but are actually caused by other vehicle systems.