Car Diagnostic Tests Made Easy (and Why You Actually Want to Pay) Updated for 2024

When our cars start clanking, smoking, and lighting up their dashboards, most of us start worrying about how hard this will hit our wallets. So when we head to a mechanic for answers and have to pay for a car diagnostic test before we even know what the issue is, we get a bit…perturbed. Especially if the big box auto shop down the block can just plug in their computer, run their car diagnostic tests, and tell us the issue for free.

There’s plenty of confusion about diagnostics and pricing. We’d like to clear that up with this post. Honesty is one of Juke Auto’s cornerstone values, which includes educating customers about our pricing. We doubt we’ll get you excited about paying for a diagnostic, but we hope to help you understand a bit more about exactly where that money is going.

What is (and what isn’t) a Car Diagnostic Test?

A diagnostic is a test of your auto’s computer and other systems. Modern cars are much more computerized than in the past, and just like your laptop or phone, it’s not always easy to pinpoint precisely what’s wrong.

A Windows style error message reading I broke

Diagnostics can test for issues with your engine, brakes, transmission, exhaust system; you get the idea. Depending on your particular needs, your technician may perform different types of diagnostic tests.

Many chains will offer to pull codes free of charge, but this isn’t a diagnostic. Pulling codes is simply plugging a scanner into the car’s computer and accessing error codes. This is great for seeing which parameters are out of range, but it’s not the same as pinpointing the problem. You can even purchase a scanner and pull codes yourself if you’d like. However, you’ll still just be left with a bunch of error codes and no way to fix them.

It’s a great first step, but to truly diagnose the issue, much more work is involved. To return to our laptop analogy, how many times have you gotten some bizarre error code when accessing a website? Unless you’re an expert with the proper training, you likely didn’t understand the information you were given.

Another analogy (because they’re fun) is to think of pulling codes as getting the zip code of where the problem lives. That’s helpful, but you’ll need to do some legwork to get the exact address of the issue. That’s where you need a well-trained auto tech to run a full car diagnostic test.

Why Do I Have to Pay for Car Diagnostic Tests?

Now that you have a better idea of what diag is, you’re probably starting to see why it’s not free. For starters, you’re paying for the tech’s time. Not only for the time they spend with your car directly but the years they put into becoming an expert at their trade.

Charging for diagnostics also helps to cover the cost of specialized equipment. This is especially true if you’ve switched to an electric vehicle.

Ultimately, a thorough diagnostic is just part of quality auto repair. Without one, you could end up paying a lot more for work that’s unnecessary or incorrect. You wouldn’t let a doctor perform surgery without providing you with a proper diagnosis first.


At Juke Auto, we’ll charge you for diagnostic work based on how long it takes to determine the issue with your car. That’s typically between a half hour and an hour, but sometimes more, sometimes less. We’ll never charge you for more than an hour of diag work without contacting you for permission first.

You may have never seen a diagnostic fee on your repair bill before. Or maybe a shop offered to diagnose for free if you had the repairs done with them. That’s because many shops simply roll the car diagnostic test into the cost of the repairs. Whether you know it or not, you’ll always pay for diag.

When Should I Get a Diagnostic Test?

A car diagnostic test is likely to be part of the process for many repairs. Whether it’s a check engine light, a new noise, or just a feeling that something’s wrong, your best bet is to get your car to a trusted mechanic as soon as you can.

You might consider having a diag done when purchasing a used car. We always recommend at least a pre-purchase inspection, which is different and separate from diag. If any issues are uncovered during the inspection, it may be worth following up with a diagnostic test to get a better idea of if the problem is one you’re willing to take on.

We hope this cleared up some misconceptions about diagnostics. If you still have questions when you bring your car in, our service advisors are more than happy to explain our rates. Contact us when it’s time for your next appointment.

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