2890 Jackson Ave.  |  Ann Arbor, MI 48103  |  M-F 8 AM - 4 PM


All About Check Engine Light Diagnostics

Car Diagnostics at Louie and John’s

We get a lot of calls where customers describe car trouble and want a quote over the phone. We do our best to help, but without seeing the car and running a diagnostic, it’s impossible to know what’s involved. Calling around for quotes is time that could be used figuring out what your car repair needs actually are, and addressing them. Comparing these phone quotes is equally inefficient; you’ll get wildly different estimates because the shop doesn’t actually know what your issue is.

When you bring your car in to Complete Auto Service, we’ll hook your vehicle up to a machine that helps us spot any performance issues that need to be fixed. Our diagnostic machines have software that accesses your car’s computer system. This is where all your faults with the car are logged. It’s simple, but it tells us a lot about the condition of your engine. We can fix your car faster when we can see what’s going on with it.

Benefits of Performing a Diagnostic

Here’s a scenario: you’re driving home from work and you notice your car just doesn’t act right. Maybe it’s misfiring or acceleration is slow. Next, the dreaded check engine light comes on. Is it the air filter? Hmm, the spark plugs haven’t been changed in a while. It could be a number of issues, and the auto diagnostic allows our technicians to pull the error log from your vehicle’s computer. The auto diagnostic eliminates a lot of the trial-and-error guessing that used to go into the diagnosing car troubles. This saves you time and money. We can find any small issues affecting your car, and correct them before they become big, expensive, emergency projects!

What Does This Test?

The very first thing we will do is plug the scanner into your OBD-II port. This generates a report of the computer codes, computer software version numbers, and critical data and sensor information. While it seems simple (and it is), there’s a lot more that goes into the diagnostic process. While codes are great, it’s not ALL the information we use to help you get back on the road.

Next, there’s a verification phase of testing, where we test various auto systems like engine pressure, back pressure, ignition, emissions. There is a lot more to running these tests than just pulling codes because this does not offer all of the information available. Next, we’ll run a verification test. This phase of auto diagnostics will test systems like engine vacuum and back pressure, the ignition system, and the emissions systems. If anything goes haywire with any of these basic systems, that’s when your check engine light comes on. Your car is telling you it’s sick and needs some care, so come in as soon as you can so the problem doesn’t become a huge expensive problem. In order to make a diagnostic determination, circuit and component pinpoint testing must be completed. We’ll work through wiring diagrams for your car’s make and model and perform electrical and mechanical tests, bi-directional control tests, and visual inspections of the areas that could be causing your car trouble.

What Happens After the Diagnostic

Once we have all of the data from the tests, we’ll research it. If it’s a known issue that regularly occurs on your make and model, we’ll find out.  There will likely be more information in the Technical Bulletin for your car that could be contributing to the problems you’re having. Once we have analyzed all the data, we’ll let you know what the necessary repairs will be, and what it will cost. We’ll even tell you what needs to be fixed NOW, and what can wait.  We’re nice like that. Repairs could range from replacing parts, rewiring or replacement of important systems, updating the vehicle’s computer, or cleaning parts under the hood.

Louie and John’s Complete Auto Service of Ann Arbor offers full vehicle diagnostics on all cars, foreign and domestic. If that check engine light has visited YOU, schedule an appointment or just bring the car in and get it car back in shape!

We also offer our Ultimate Family Value Plan for Car Care, which saves you HUNDREDS on regular car maintenance, reducing the need for big repairs:

When you join our Plan, you’ll be one of our privileged clients that will get to enjoy hundreds of dollars in savings over the next 18 months. As a member, you’ll receive a special Ultimate Family Value Plan Card that is filled with all of the following car care products and services:

  • FREE – UNLIMITED Oil Changes (A $128.00 Value)
  • FREE – UNLIMITED Pair of Wiper Blades (Up to a $24.95 Value)
  • FREE – UNLIMITED Brake Pads with Brake Service (A $54.00 Value)
  • FREE – UNLIMITED Brake Inspection with Tire Rotation (A $51.40 Value)
  • $45.00 off – 30,000, 60,000 or 90,000 Mile Service Packages
  • $50.00 off – Exhaust System Repair
  • $15.00 off – Power Steering Flush & Fill
  • $15.00 off – Cooling System Flush & Fill
  • $50.00 off – Transmission Power Flush & Fill

You’re not limited to using your Ultimate Family Value Plan Card on only one car. So even if you’re driving a newer car and may not need all of the services on the card, you can give it to your spouse or a friend and let them use it to save money on any repairs they may need.

Add up all the savings and you’ll find that you could easily save up to $484.75 over the next year! But even if you didn’t use all of the services on the card, the money you’ll save on the UNLIMITED OIL CHANGES alone are well worth the introductory price of $209.95.