Establishing A Diagnostic Plan

Once all of the pre-diagnostic criteria has been satisfied, a logical diagnostic plan should be followed. A logical, well organized diagnostic plan will help avoid improper diagnosis, unnecessary parts replacement and lost diagnostic time. The productivity of the technician can also be improved by following a logical, common-sense approach to problem solving. The following steps are recommended to form a diagnostic plan:

• Verify the Customer Complaint - This step is the most important, but also the most overlooked. The focus should always be on the exact customer concern. Make sure that the customer complaint is not a misunderstanding of proper vehicle operation. This step can avoid unnecessary diagnosis and lost time. Also make sure that the conditions under which the concern has occurred are duplicated. For example: If the customer is complaining about a shifting concern after a cold start, then the vehicle should be road tested under those conditions.
• Analyze the Problem - Once the complaint has been verified, then all available resources should be used to find the "root cause" of the complaint. Start out by checking technical service bulletins. Use the DISplus or GT-1 to access the diagnostic program and perform Diagnostic Test Modules where applicable. Wiring diagrams should also be used when needed.
• Isolate the Problem - Now, the problem can be narrowed down into the final steps of diagnosis. Using proper tools and procedures, the technician can "Isolate" by using the process of elimination and common sense. Perform all necessary electrical checks such as Voltage Drop, resistance measurements etc.
• Repair the Problem - Once the concern has been correctly identified, perform all necessary repairs.
• Verify the Repair - Make sure the customer concern has been rectified. Road test the vehicle under the same conditions whenever possible.