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Car Diagnostic Test

What Can a Car Diagnostic Test Tell You?


Daniel McDonald
Daniel McDonald8 min read
What Can a Car Diagnostic Test Tell You?

If the check engine light in your dashboard comes up, it is time to run a car diagnostic test. Drivers need to keep their cars in proper order to ensure they encounter no obstacles on the road. The last thing they want is a severe malfunction with their cars that can cost them hundreds of dollars.

So, to save yourself from all this hassle, you need to go for a car diagnostic test as soon as you see your check engine light blinking. You don't need to go for car diagnostic tests only when the check engine light comes on, and you can get your mechanic to run these tests during the regular maintenance and checkup.

Also, you don't necessarily have to go to a technician to perform a car diagnostic test. You can do these tests with the right tools and mechanical knowledge. While most drivers need only go for a diagnostic test when seeing the warning light, you can also run these tests routinely.

This way, you can uncover minor problems with your car and resolve them before they become significant issues. But what can a car diagnostic test tell you? Let's find out more about it, but before, we will give a small overview of the car diagnostic test.

Car Diagnostic Test: Overview

The car diagnostic test entails finding out the problem with your vehicle through the maintenance and analysis system. This test uncovers the potential issues causing the check engine light on your dashboard to turn up.

The light is a part of the onboard diagnostic system that indicates potential problems with your car. Over the last few decades, this technological advancement in the automobile industry has benefited technicians and car owners.

Computerizing the car's components makes it easy for technicians to run tests and discover possible issues. Modern cars have sensors, built-in processors, and other critical components. You can use the car diagnostic tool quickly identify the problems with your car engine, ignition coils, brakes, airflow, etc.

These tools have specialized software that allows the mechanics to diagnose car issues quickly. Let's understand how the car diagnostic test works.

How Do Mechanics Perform Car Diagnostic Tests?

As soon as you see the check engine light turn on your dashboard, you would head over to your nearest dealer shop to run the engine diagnostics test. Their technicians will have the appropriate equipment to diagnose the issue by reading the DTC (diagnostic trouble codes).

What are Diagnostic Trouble Codes?

The diagnostic trouble codes are the five digits that tell you about the car's particular issue. These codes come up on the scanning tool after connecting it to their cars' onboard diagnosis system.

The code comprises numbers and letters which tell whether there are typical problems or something that would require the vehicle to go to the manufacturer for repairs. It is better to get your local mechanic to run diagnostic tests as soon as the light comes on.

The technician's equipment will help them understand what is wrong with the vehicle since the car's computer can communicate with it. These advanced types of equipment will determine the areas that might have the fault, including your gas tank, transmission, or any other major components.

As a result, the mechanic can repair the issue correctly and quickly. Also, the mechanics perform the car diagnostic test to ensure the sensors and other processors are operating properly.

What Can the Car Diagnostic Tests Tell You?

Now that you know how the car diagnostic tests work and they are a handy way to identify problems with your car, you might think that it will tell you about all the issues. However, that is not the case since the engine diagnostic tests only cover a range of issues.

These issues are limited to the areas with which the equipment can communicate via engine sensors. If there are any other issues with the cars, the technicians will have to use them any other way.

Things That the Car Diagnostics Test Tells You

Here are a few things that you can find out from the car diagnostics tools:

  • The car needs an oil change

  • Oil or coolant levels are down to a significantly low level

  • A worn-out oxygen sensor can be why the emissions test fails during engine diagnostic tests.

  • The coil pack is not working correctly or has failed completely

  • The sensors for mass air flow, air intake, or other functions have stopped working.

Things That the Car Diagnostics Test Doesn't Tell You.

Despite the ease it offers, there are a few things that car diagnostic tests cannot identify and tell you. Here is a list of them:

  • The tire size is not correct as per the vehicle

  • The rotor, brakes, or any other component of the braking system is not working

  • The alignment of the car is out

  • The headlight bulb is burning out or not working at all

  • Whether you are using the correct fuel octane

When Should You Go For a Car Diagnostic Test?

Most people tend to believe that the car diagnostic test is something you should go for on a routine basis. While it is something you can get done with your scheduled maintenance appointments, it is unnecessary.

Generally, if your vehicle is operating without any issues, you don't need to go for an engine diagnostics test. But if the check engine light in your dashboard is coming up, it means you should get a professional to check your car.

The check engine indicates an issue with your engine, gas cap, or other significant components. However, there can be times when there is no light on the dashboard, yet you feel the vehicle is not working as it should be.

Since you know your vehicle more than anyone else, you would probably notice when you smell something strange or feel the car's engine is making some strange noises. You can head over to the mechanics, and they can run a simple diagnostic test for you.

Let's go over some signs that indicate you need to perform a car diagnostic test and some that you can skip.

Signs That Tell You Need To Get a Car Diagnostic Test

Here are some possible signals that indicate you need to get a diagnostic test:

  • When the light for the check engine comes on

  • The other warning lights on the dashboard start turning on and off, like the battery light, or more

  • The engine is not performing as it should, such as consuming too much fuel, producing a lot of smoke, or even backfires

  • There is some repair work done which is causing the light in the dashboard to turn on

Signs That You Can Skip for a Car Diagnostic Test

Not all signs mean that you rush to get a diagnostic test. There are a few minor signals that you can ignore, such as:

  • You just changed the oil, causing the warning lights to come up

  • There is no problem when driving the car

  • No warning lights in the vehicle are flashing

  • A service technician is recommending it to push the cost up

What Should You Do If Your Check Engine Light Starts to Come on?

The engine light on your dashboard does not necessarily mean you go for a diagnostic test, and the are multiple reasons it might come on in different cars.

The light might not only come up when there is an issue with the car's engine but will also start to blink when there is a problem with ignition coils or other components. Let's look at the few possible scenarios where the engine light will come on.

The Performance is Not The Same When the Lights Illuminates and Stay On

If this scenario happens in your car, it indicates a significant fault in your engine management system or the emission control. Both these parts are essential for cars to function smoothly.

If you experience this scenario, then this indicates that the car is not safe to operate, and it could come to a halt at any time. Therefore, you should head over to a repair shop as soon as this happens.

The Light Comes On But Only in Specific Situation

Occasionally, you will notice the engine light come on when you are driving in the city, but it goes off as soon as you get on the freeway. The light might also flicker sometimes. So, if you face such a situation, you should check if there is any change in the car's performance.

In case you notice a difference in the performance, you should drive it to the nearest service center so they can have a look at it.

If there is no difference, you can continue to drive as standard. But, it is best to visit the service center as soon as possible since the cars might not start or die in this scenario.

The Light Stays On Continuously

There is also a possibility that the engine light will come on and stays on constantly. However, there would be no difference in your car's performance, and this scenario can indicate a faulty emission control system in the car.

If this happens, then this means that the car's computer, which monitors the emissions system, is having some problems. As a result, it might turn off the AC or other less crucial components of the cars. This condition is known as the limp-home mode, and it is better to get a local technician to service your car.

The Light Comes on And Blinks When You are Driving Constantly

Last but not least, many vehicle owners might notice that the light will come on and continue to blink steadily. It would be best if you did not mix this blinking of the engine light on your dashboard with a flicker.

If there is one or more flash in a second, this indicates a severe problem with your vehicle. Usually, the emission control systems fail to work correctly, and they cause the engine to misfire to the extent that it harms the catalytic converter whenever the light flashes.

The catalytic converter plays a crucial role in your car's various systems. The engine light blinking indicates that it is overheating to the extent of turning red. In some extreme instances, the overheating of the catalytic converter may also start a small fire at the bottom.

So, you need to stop your car immediately and get someone to tow it to the nearest repair shop so the professional can start the repairs as soon as possible.

Common Reasons for the Check Engine Light to Come Up

There can be many reasons which can lead to the engine light coming on. However, a few of them are more than ordinary, such as:

  • Your oxygen sensor is not working correctly and needs a replacement

  • The gas cap is loose, and tightening or replacing it might do the job for you

  • The spark plug wires are failing or are faulty

  • The catalytic converter is damaged and would need a replacement

  • The airflow sensor is not working correctly and you would need to replace it

Final Word

The onboard diagnostics system in modern automobiles plays a vital role in keeping their vital systems and components safe. They can notify you about possible issues with the transmission, engine, etc., to keep the vehicles in good condition.

So, if the light turns on, you should head over to the nearest dealer shops to get the issues checked. They have the expertise and tools for identifying issues that the light in your dashboard is indicating. The experts will carry out the complete investigative process, including visual inspection, and then let you know the best possible course for the repairs.

You can conduct the test yourself if you have the right tools, such as a code reader and complete mechanical knowledge. Also, you can complete investigative work to ensure all the systems in your car are operating in optimal condition.

However, professional experts can inform you about the repair work needed to fix the car. You might be good at identifying problems that cause the engine light to come on.