What Is a Diagnostic Test on a Car?
Think for a minute about everything your modern car does besides simply getting you through your daily commute and errands regimen. It monitors your tire pressure, provides real-time traffic information and even assists with parallel parking — and that’s just scratching the surface.
From automatic emergency braking and seat position recall to Bluetooth that enables hands-free calling and music streaming, modern cars are equipped with sophisticated computerized systems that keep us safer, more comfortable and even entertained as we drive. All these features rely on a network of sensors and computers that constantly monitor your vehicle’s performance and send out alerts if any issues are detected.
Diagnostic testing is the process of scanning your car’s computer to pinpoint an issue, which in turn helps your technician find and solve the problem quickly.
In this post, we will take a closer look at diagnostic testing, including:
- The purpose of a car diagnostic test
- What’s included in your diagnostic test
- How much it costs to get a diagnostic test
What Is a Car Diagnostic Test?
Given the complexity of most modern cars, popping the hood and looking around sometimes isn’t sufficient to see precisely what’s wrong. A diagnostic test is a computerized analysis of your car’s systems and parts.
Cars have been equipped with on-board diagnostic systems (OBDs) for decades. The computer-based systems were “originally designed to reduce emissions by monitoring the performance of major engine components,” according to OBD Solutions. “A basic OBD system consists of an ECU (Electronic Control Unit), which uses input from various sensors (e.g., oxygen sensors) to control the actuators (e.g., fuel injectors) to get the desired performance. The ‘Check Engine’ light, also known as the MIL (Malfunction Indicator Light), provides an early warning of malfunctions to the vehicle owner. A modern vehicle can support hundreds of parameters, which can be accessed via the DLC (Diagnostic Link Connector) using a device called a scan tool.”
There are two primary OBD systems in today’s vehicles. Cars manufactured between 1981 and 1996 use OBD-I systems. Since about 1994, most cars have come equipped with OBD-II systems. These are more standardized systems that meet requirements laid out by the Society of Automotive Engineers (SAE). OBD-II systems allow mechanics to connect to a wide variety of vehicles without needing multiple adapters.
How Does a Car Diagnostic Test Work?
A car diagnostic test is typically triggered when the check engine light in your car comes on. Your mechanic will connect the scan tool to your car’s OBD via a port, usually near the steering wheel.
Your mechanic will connect a scan tool to your OBD port, which allows them to view diagnostic trouble codes (DTC). Each DTC begins with a letter that corresponds to the system where the issue may be found. For example, if the problem is with the powertrain system, the code will begin with P.
These codes give your mechanic information about the nature and location of the problem, allowing for a precise diagnosis and efficient repair process. Your mechanic will interpret the codes using diagnostic software and use that information to inspect the part of your vehicle that may have a problem.
Once the technician is able to identify the issue, they will reset the light and go over the information with you. The solution will typically involve repairing or replacing the problem parts.
What Can a Car Diagnostic Test Tell You?
A car diagnostic test offers a wealth of information about what’s going on inside your vehicle. The main purpose of these diagnostic tests is to:
- Identify minor problems before they escalate to major issues
- Identify major issues before they become catastrophic
- Pinpoint specific components that need attention
- Assess engine performance and efficiency
- Give you a baseline look at your car’s health
A diagnostic test can reveal issues with all the major systems in your car, including the engine, brakes, electrical system, fuel and emissions, airbags and exhaust system. It can also diagnose performance issues, giving you clues as to why you might be experiencing reduced power.
How Often Should You Get a Car Diagnostic Test?
Whenever you see the check engine light, head in right away for a diagnostic test. It may be that your gas cap came loose, or there could be trouble with your engine. A diagnostic test will give you the answers you need. If you notice issues in your car’s performance or functionality or pick up on odd noises or smells, a diagnostic test can also be useful.
Apart from trouble-shooting visits, an annual diagnostic test is recommended as part of your routine maintenance schedule.
How Much Does a Car Diagnostic Test Cost?
The cost of diagnostic tests varies depending on your car’s make and model, but on average, they will cost about $80-$100.
It’s tempting to ignore that check engine light, but putting off services will cost you more in the long run. Many problems, like worn brakes or degrading belts, progress slowly over time. By taking your car in for an inspection as soon as something seems off, you’ll not only save time and money, but you’ll also help extend the life of your car.
If it’s been a while since your last diagnostic test, or if you notice that pesky check engine light, make an appointment at your nearest Boyce Auto Repair location. We’ll go over the results with you and recommend the right solutions for your vehicle so you can get back on the road quickly and safely.
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