The Diagnostic Process

… Money Well Spent

How much for a diagnosis?

I’m asked this question, on average, at least once a day. This over-simplification illustrates a lack of understanding of the complexity of the modern automobile.

The appearance of a “check engine” or “service engine soon” light on the dash is the most common cause of this question, but I might also be asked in relation to a performance problem, unusual odor, poor fuel economy, or just curiosity as to the condition of the vehicle.

We’ve been led to believe that the automotive service industry has a magic machine that just spits out the answer to whatever is wrong with your vehicle.

The code reader is not the magic bullet

The internet and the discount service sources sing their praises. In reality, most code readers are very limited, only capable of retrieving a diagnostic trouble code from one or two of a vehicle’s control modules and giving a generic definition of the problem, and allowing you to turn off that pesky “check engine” light.

In reality, this service may end up costing you more when valuable information is flushed along with the code and corresponding light.

What is really involved in an accurate and cost effective diagnostic process? The vast majority of the vehicles on the road today have numerous computers or control modules, all linked together and communicating with each other.

A successful diagnostic process requires:

  • Detailed information from the customer regarding the nature of the concern
  • A well trained and highly skilled technician to navigate the process
  • Information specific to the vehicle being diagnosed, and
  • A variety of diagnostic equipment and the knowledge on how and when to use these machines

Ultimately, it’s not the cost of the diagnosis that counts, but the final cost when the vehicle is accurately diagnosed and repaired. One incorrect part will often exceed the cost of diagnosis, and the vehicle still isn’t fixed.

An Example

A customer came to me recently and asked the price to replace her EGR (exhaust gas recirculation) valve. She felt that service was needed because a quick lube had scanned her computer and the code indicated that the valve was bad. This particular model is notorious for plugged EGR passages. Without further testing, beyond the computer scan, there is a good chance that replacement of an expensive EGR valve would not have fixed the problem, the same computer code would have returned, and additional expense would be incurred to finally repair the problem.

The doctor vs. the automotive technician

We often use the analogy of the doctor’s office for how and why a diagnostic process should be performed.

We accept that a doctor will need to schedule some time for us to come into the office so that he/she can examine us. We need to provide some detail as to what is ailing us, so the doctor can focus on the source of the problem. We understand that research and the use of specialized test equipment is necessary, and it will require a trained technician to analyze the data from the specialized equipment.

And yet, we have trouble accepting that all of the above statements are equally true when substituting the word automotive technician for the word doctor…But they are!

We don’t go to the supermarket pharmacy for a free MRI so why do we go to the cut-rate parts house for a free computer scan?

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