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What Is The Purpose Of Diagnosing A Car

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  • 31-08-2022
What Is The Purpose Of Diagnosing A Car

What is the purpose of diagnosing a car? This article looks at when you should get a car diagnostic test and which parts of a car are tested.

Should I get a car diagnostic test?

The reason for general diagnostic tests and engine diagnostics tests is to assist with the identification of any issues with a vehicle before they grow into more severe problems that will have more serious effects on the car's performance.

If you take your vehicle in for an annual vehicle diagnostics test, then you can find out about minor problems that may be affecting your vehicle and the way it performs that would otherwise not be picked up by your car's engine control unit until it is far too late.

In addition to this, if you go through the process of conducting a check on a car that has been used, then the car's ECU will store all the previous information from the manufacturer, as well as previous data pertaining to the vehicle's performance. This will provide plenty of information that you can use for making an informed inspection.

The standard time that it takes to have a standard diagnostics test is around an hour. This is a very small amount of time to sacrifice in order to ensure that your vehicle is running with as minimal problems as possible and to locate any issues that could potentially grow and cost you more money in the future.

What is a Car Diagnostic Test?

There have been various different technological advances in the field of automotive mechanics over the past decades, and one of the most beneficial both to consumers and the technicians working on vehicles is the computerisation of a car's components.

By using specialised software, modern car diagnostic tools are capable of very quickly and accurately locating any problem areas within a car's engine or anywhere else in the vehicle. This is done through a combination of built-in sensors, microchips, and processors.

What Will A Car Diagnostic Test Tell You?

A car diagnostic test can make a major difference not only for your vehicle but for your wallet too.

Having a diagnostics test completed can help with spotting issues with your car early before they become major issues, so you don't have to pay out a lot of money for repairs.

The common vehicle diagnostic test will let you know about a range of issues that your car may be experiencing in areas such as exhaust, brakes, throttle, transmission, engine management, ignition coils, and more.

It is common for vehicle diagnostic tests to focus on the car's engine, but depending on the vehicle that is being examined, the diagnostic results will also offer data relating to other aspects of the car, such as the tyres, lights, and comfort controls.

There are also some very specific problems that be identified through a diagnostic test, such as poor ignition timing, uncontrolled build-up in the combustion engine, poor performance from the fuel injection system, ignition coil firing failure, notably low or high rpm levels, and low engine coolant levels.

What Is The Purpose Of Diagnosing A Car?

What Parts of a Car Are Tested?

Car diagnostic tests are capable of analysing various different sections of your vehicle. Below is a list of the different zones that the diagnostic tests will check for:

  • Issues with your car's engine or individual components
  • Problems with your vehicle's transmission and responsiveness
  • Any issues with the brake responsiveness
  • Any potential faults or contamination with the vehicle's exhaust system
  • Signs of breakage or wear and tear associated with major vehicle components such as the throttle, ignition coils, and fuel injector

Car diagnostic tests are perfect for helping drivers assess what state their vehicle is in and locate any issues, but it is important to remember that diagnostic tests are not always one hundred percent accurate. In many cases, the test is unable to tell the tester or the technician exactly what the issue is.

Instead, the test is used as a way to narrow down the exact location of a problem or a potential error. This is done so that mechanics can identify and take care of any issues much quicker for the driver.  

How Do Car Diagnostic Tests Work?

Diagnostic tests work by using a vehicle's engine control unit. This can be found in almost all modern cars.

The engine control unit, also known as the ECU, uses sensors that are installed all throughout the vehicle in order to locate any issues when they occur.

The issues that the ECU is capable of picking up can range from increased engine temperature to faulty ignition coils that aren't firing.

Each error that the ECU can identify generates a specific and unique error code that is then sent to the car's dashboard and indicated by the corresponding warning light.

However, even though the dashboard is capable of letting you know that there is an issue somewhere in the car, the complete extent of the problem can truly only be gauged by using specialist vehicle diagnostics equipment.

This equipment reads error codes that can then be used by trained technicians to identify the issue at hand. 

How Do Car Diagnostic Tests Work?

How Often Should a Car Undergo Diagnostic Testing?

Despite what people may tell you, in actuality, you do not have to wait until the check engine light appears on your dashboard before you get a car diagnostic test.

If, when you are driving around, you feel or hear something in your car that just seems a little "off" or "wrong", then you are welcome to visit a mechanic that will use diagnostic testing in order to uncover exactly what the problem is. 

Many vehicle technicians will recommend that you should take your car in for a diagnostic testing check at least once per year. 

This will ensure that any minor problems with your vehicle that you may not have noticed due to them not triggering the check engine light can be identified and fixed so you can drive safely. Diagnostic testing is also a very useful tool when you are looking at purchasing a used car.

Whether you are purchasing from a professional car dealer or a private seller, you should always agree to a vehicle diagnostic test before you commit to buying a used car. If the seller does not want to agree to these terms, then they are likely to be hiding something, and you should find a seller elsewhere.

How Long Does It Take to Do a Car Diagnostic Test?

The length that a car diagnostic test will take is dependent on what exactly turns out to be wrong with your vehicle. But, you can expect, on average, for a diagnostic test to take somewhere between sixty to ninety minutes.

If the issue turns out to be something a little more complicated, then the mechanic may have to remove some components from your car in order to gain further access so they can do more testing. In situations such as these, you should expect your car to be tested for somewhere between two to three hours.

Although, the length of time that a car diagnostic test will take is truly dependent on the specific technician that is doing the testing.


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We offer a complete range of Jaguar servicing for Peterborough and the surrounding areas including: Huntingdon, Stamford, Kettering, Northampton, Crowland, Market Deeping and Grantham.