Why Do I Have to Pay Diagnostic Fees for My Car?

Fairfax, Virginia – Just the other day I visited an orthopedic surgeon for my third post-surgery exam. The surgeon asked me a few questions, moved my kneecap around a bit, flexed my leg and told me everything was fine. Forget the fact that my knee was still sore. That, he said, would resolve in time. After waiting more than an hour to see the doctor, I saw him for less than five minutes, and all he said was, “Looks good.” I left frustrated with the residual pain in my knee and the seeming waste of time in my doctor’s office.

Frustrated as I was, I never once thought that the surgeon should not be paid for his time. Months earlier I visited that same office with a complaint of pain in my knee. The doctor performed an exam and ordered an MRI. When the test results were in, I visited again so that he could explain what he found. He got paid for those visits too. See, while I was quite familiar with the pain I was experiencing, I could not have interpreted the results of the MRI myself. Neither could I have planned a course of action. I needed the surgeon’s years of training and expertise (not to mention the MRI machine) for an accurate diagnosis.

After all, you don’t pay a doctor to tell you that you have a stomach ache or headache or knee pain. You pay a doctor to tell you why. And you don’t pay a dentist to inform you of your sore tooth but to diagnose what is wrong inside your mouth and to know what to do about it. You could ask a friend or neighbor for their opinion, but you probably wouldn’t get the same type of answer that comes with years of training and experience and thousands of dollars of equipment to go along with it.  So why would it be any different when it comes to diagnosis of your car, truck, or SUV?

After all, would you ask an HVAC professional to inspect your furnace for free? How about an arborist – a tree surgeon? Would you expect an exam and diagnosis of your failing ficus tree to be free of charge? Probably not. You might say, “But those professionals come to my house, whereas with my car, I am taking it to the shop myself.” And you would be right. When professionals make house calls you expect to pay them for their time.

But have you considered the costs associated with the shop to which you are delivering your vehicle? Besides the actual time a technician spends looking at your car, there is a mound of overhead expenses just to keep the shop doors open and lights on: a lease, insurance, utilities and more. There are hundreds of thousands of dollars of specialized diagnostic and repair equipment. And there are trained technicians, each with thousands of dollars of tools and years of experience. What you are paying for is quality service. And an accurate diagnosis is just as much a service item as if the technician had manually repaired or replaced a part on your car.

So why would you expect that service to be “on the house”?

The trouble with trouble codes

One of the reasons many of us have a tough time swallowing diagnostic fees at an auto repair shop stems from a common misconception. Modern vehicles are equipped with a network of computer modules that continuously monitor vehicle systems. When something goes wrong in a system, a computer module stores a Diagnostic Trouble Code (DTC) and often alerts the driver through a warning light on the dashboard. If the Supplemental Restraint System (SRS) that controls the airbags has a problem, the airbag light on your dash turns on. If an oxygen sensor goes bad, your check engine light comes on. Our cars are smart enough to tell us when something goes wrong.

But that is where the misconception begins. It is true that when a special scan tool is connected to a vehicle’s data link connector, those trouble codes stored in the computer can be read. So, many folks believe that by simply plugging in and reading the scan tool, a technician can easily diagnose an issue. How hard can that be? And how much time could it possibly take? The computer is doing all the work. Right? Wrong.

You take your car in for service because your SRS warning light is on and because you correctly assume that your airbags might not be operational. A technician plugs in a scan tool and finds a DTC leading to a specific circuit in the system, say, the passenger seat belt retractor. Now what?

The popular notion is that the technician’s job is done. Diagnosis performed. But the truth is it has only begun. What started with a customer complaint (“My airbag light is on”) led to a diagnostic scan. But that is still the beginning of a diagnosis. The technician still does not know what the problem is, only where it might be found

Pinpointing the problem

Diagnostic scan tools do not simply spit out a diagnosis. So what does a diagnostic scan show? Scan tools read and display the DTCs stored in the computer. But the DTC is a code: a letter and  a few numbers. P0135 , P0340 and B1881 are examples of DTCs for (respectively) a faulty oxygen sensor, camshaft position sensor circuit, and passenger seat belt pretensioner. In each of these cases, the DTC does not imply a problem with that component specifically, only that there is a fault in the circuit in which the component resides. The DTC does not give a specific diagnosis any more than an MRI tells a patient what is wrong with his knee.

Once a technician receives the DTC from a scan tool, (s)he still has to perform a series of pinpoint tests to determine the exact cause of the fault revealed by the code. In the case of an oxygen sensor, the correct sensor needs to be identified (cars often have four oxygen sensors). With a camshaft position sensor fault, the problem could be with the sensor, the wiring, or even the powertrain control module. And in our SRS “airbag light” example, the fault could lie with the pretensioner, the wiring, or a bad ground. A technician needs to “pinpoint” the problem beyond a simple scan.

But doesn’t the auto parts store scan for free?

My wife loves when the grocery store gives away goodies. Of course, we inevitably spend a half hour scouring the store for that freebie only to find out it was a bite-sized breakfast bar worth a buck. Just because it’s free doesn’t mean it is of much value.

In the same way, a scan by a salesperson at a nearby auto parts store might provide a morsel of information, but it does not tell the whole story.

First of all, a scan tool is not just a scan tool. They are not all the same and do not all give the same data. Some scan tools – the ones used in repair shops – cost thousands. The ones used at the parts store? Not so much. In fact, you can purchase your own basic scan tool for less than a hundred bucks. It just won’t tell you much. And if the expensive version only provides the beginning of a roadmap to diagnosis, how much do you think the cheap ones provide? A scan tool itself is not a diagnosis for very many things. It is a piece of information in the diagnosis chain. What you will not get at the auto parts store is a series of pinpoint tests to find the fault. And their scan tool will not clear the old DTCs from the computer after repairs are complete. At the store, you will get a part sold to you based (most likely) on an assumption of what is wrong. If the part does not fix the problem, you will get a recommendation for another part. That is why the auto parts store does a free scan. To sell auto parts.

In the end, it is often less expensive to pay a technician to diagnose an issue with your vehicle than it is to throw parts at the problem. And besides, if you opt to have the work done at the shop, the price of the diagnosis is often applied toward the fix, or at least overlaps with the repair costs. If you choose instead not to have work performed on your car, a diagnostic fee ensures that the repair shop is reimbursed for the time, tools, and knowledge it provided in presenting an accurate diagnosis.

So, how much does it cost to run a diagnostic test on a car?

Most shops charge an hour of labor at their flat rate – generally somewhere between $80-100 at an independent garage, a bit more at a dealership. It pays to allow the pros to diagnose and repair what is likely one of your biggest investments: your vehicle. If you experience a problem with your car, take it for an accurate assessment at a trusted shop near you.

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