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Six steps to a sound diagnostic strategy

By Bob Chabot, Manic Media LLC

James E. Wilson of Bosch USA was a presenter at MACS 2016 Training Event and Trade Show in Orlando, FL this past February he left us with some great information including these six steps to sound diagnostic strategy.

Jim Wilson of Bosch USA

Jim Wilson of Bosch USA

“Having the correct tools and using them properly is essential, but it’s also critical to follow a sound diagnostic plan and process,” Wilson noted. “Beware of flow charts; they can be confusing and often will not fix the vehicle. He suggested these key steps as part of the diagnostic process:

  • Step 1: Verify the complaint — Too many technicians try to find out what’s wrong, when they should begin with knowing what’s right.
    Step 2: Narrow the search — Use a scan tool to perform an all system sweep for codes and communication to determine known goods and bads.
  • Step 3: Research the known issues — Document the codes that need to be addressed. Use quality information sources to understand the repair path.
  • Step 4: Create a prioritized plan to test the system — For each DTC, read service bulletins and wiring diagrams, plan necessary reflashes, use tools that test what you are looking for, and determine which components may need replacing.
  • Step 5: Remember the basics when performing system tests — Examples include checking the battery condition and missing or blown fuses.
  • Step 6: Verify your work — Check that your work has completely resolved the original problem(s) you verified in Step 1. Then ensure your customer is satisfied.


Wilson ended the seminar with several real world A/C repair case studies that demonstrated the diagnostic strategy process and tools used. “Remember: If you approach a vehicle in a haphazard manner, as too many do, you’re likely to perform an incomplete repair. Following the diagnostic process is crucial to being the expert your customers pay you to be.”

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