Diagnostic Procedure consists of the following:

OVERVIEW

5-Step Diagnostic Procedure is a proven method to fix the vehicle right the first time, every time.

While it may be tempting to short-cut these steps to save time, you will find that omitting or not following these steps will actually cost you more time and possibly jeopardize the repair.

The 5-Step Diagnostic Procedure consists of the following:

  1. Verify the customer’s concern
  2. Analyze the customer’s concern
  3. Diagnose the customer’s concern to determine the root cause
  4. Repair the diagnosed concern
  5. Verify the repair

The first three steps represent important confirmation and diagnostic procedures to help you:

  • Review and confirm the customer’s concern as communicated by the customer to the service advisor or to you.
  • Investigate the system that is not operating properly and determine the reasons for the malfunction.
  • Use sound diagnostic procedures to eliminate some of the possible causes

Once you’ve determined the root cause, you can efficiently repair the concern and verify your repair.

STEP 1: VERIFY THE CONCERN

  • Guidelines to verify the customer’s concern are:
  • Do not disassemble, test or begin the repair until
  • you have verified and narrowed down the
  • concern.
  • Experience the symptoms first hand by trying to duplicate the concern as noted by the service advisor (For example, operate the vehicle, in the same manner, described simulating the same temperature range or road conditions).
  • Conduct a visual inspection or use a diagnostic tool, where applicable.
  • Do not erase any DTCs or Freeze Frame data until you have recorded the occurrence.

Verifying the concern will result in one of these outcomes:

  1. You were able to verify a legitimate concern;
  2. You have verified the concern, but the vehicle is
    operating normally and within manufacturer’s
    specifications so that no repair is needed; or
  3. You cannot verify the concern at this time.

  4. Note: If you cannot verify the concern or find that the vehicle is operating properly, contact the service advisor for follow-up with the customer and document your findings on the repair order. To only return the vehicle to the customer as no trouble found (NTF) may not resolve the customer’s concern.

    STEP 2: ANALYZE THE CONCERN

    Once you have verified that a malfunction exists, you can begin to analyze the customer’s concern.

    Important questions to help you analyze the concern are:

    •  Is the vehicle functioning as the manufacturer intended?
    •  Have there been previous repair attempts for the same concern?
    •  Are previous repairs the cause of the new concern?
    •  Are there any aftermarket parts or accessories installed that are influencing this concern?
    •  Are there any open campaigns or recalls that apply to the concern?
    •  Are there any Technical Service Bulletins,

    By analyzing the concern, you will be able to determine that:

    • The concern is operating within normal range and no repair is needed.
    • The concern has been attempted before, which may help you narrow down what has been done and suggest what to do next.
    • A previous repair or aftermarket parts may be the cause of the concern.

    Note: If this is a second repair attempt by you or someone else:

     

STEP 3: DIAGNOSE THE CONCERN

Having completed steps 1 and 2, you now need to determine the root cause for the concern. Formulate a simple and logical strategy to diagnose the condition.

  • Prioritize your findings based on most likely root causes.
  • Use Special Service Tools, such as tester, or diagnostic equipment to help diagnose the concern.
  • Conduct research for information that applies to the concern on KGIS or GDS.
  • If applicable, study wiring diagrams to check for a common cause for the concern.
  • If you are uncertain about what is good or bad, compare results with known good parts.

Document your findings on the repair order including:

  • Tests performed Test results
  • Expected specifications and results
  • Whether results are within or outside of

specifications.

Your diagnosis will:

  • Establish the foundation for your repair.
  • Provide necessary information for someone else to assist or to perform the repair in your absence.

should this concern escalate to a higher level?

If you cannot find the root cause, stop and return to step 2 to review your analysis. If possible, discuss the concern with another technician or your shop foreman. For further assistance.

Note: If you have spent 30 minutes or more diagnosing a concern without finding the root cause, notify your service advisor and contact Shop Formen for assistance.

STEP 4: REPAIR THE CONCERN

With the concern verified, analyzed, and diagnosed, you are now ready to perform the necessary repair.

Always follow the repair procedures outlined in the Repair Manual.

Unless the repair procedure is not specified.

  • When replacing parts, use only parts applicable to the VIN, production date, and trim code for the vehicle.
  • List what you repaired in detail on the repair order.
  • After the repair has been made:
    Verify the repair to confirm that the concern no
  • longer exists or will not reoccur.
    Try to replicate the concern as you did in step 1
  • when you verified the concern.
    Always allow time for managed systems to
  • perform “self-diagnosis”.
    Also, check to see that no new concerns appear.
  • Make sure that any DTC is erased and that it does not reset.

Note: Managed systems such as the Powertrain Control Module (PCM) often require lengthy road tests to complete system “self-diagnosis and readiness testing”. Always consult the information in Repair Manual or the Available Diagnostic Scanner when evaluating these types of systems.

Following this 5-Steps Diagnostic Procedure will not always ensure that you will be able to resolve the concern. Occasionally, you may misdiagnose or may not be able to resolve a concern.

However, not following the 5-Step Diagnostic Procedure will certainly magnify the probability of not being able to properly diagnose and resolve the concern.

Customers unhappy with the repair will not likely bring their vehicles back to your Repair Shop. Therefore, it is extremely important that you follow the above true 5-Step Diagnostic Procedure to ensure that the vehicle is fixed right the first time, every time.