How Can I Diagnose My Car? Here’s How To Be A DIY Mechanic

How Can I Diagnose My Car? Here's How To Be A DIY Mechanic

Your car’s been making a strange noise lately. Or perhaps the “check engine” light has come on and won’t go away.

While you might think that you need to take your car to a mechanic, it usually helps to be able to diagnose what’s wrong with your car yourself.

How can you diagnose your car’s problems? One of the best ways to find out what’s wrong with your car is to use an OBD2 scanner.

This is a valuable tool that can inform you of any repairs that need to be  made on your car.

Some tools even tell you about the repairs you can do yourself and which ones are best left to your mechanic. With that in mind, let’s explore how to diagnose your car. 


What To Do When The “Check Engine” Light Comes On

What To Do When The “Check Engine” Light Comes On

One of the most common situations that cause people to want to diagnose problems with their cars is when their “check engine” light comes on and doesn’t go off.

This usually results in them taking their cars to the mechanic, but it’s more cost-effective to find out what’s wrong with the use of an OBD2 scanner.

When this light comes on in your car, it means that your car’s on-board computer has found a problem with the engine.

Often, the reason why this light has been activated is that there’s a problem with a faulty sensor.

The good news is that if you know your way around your car you’ll probably be able to replace the sensor without having to go to your mechanic. 

To use an OBD2 scanner, plug it into your car’s OBD2 port which is located within close proximity to the steering wheel column. It will scan your car and communicate with your car’s computer.

When it gets the error code that’s causing the “check engine” light to come on, it will be displayed on the scanning device.

You will then have to find out what the code refers to so that you can find the location of the fault. Luckily, many OBD2 scanners will have a database of thousands of codes so that you can find out what yours means. 

How To Notice Car Problems Without A Scanning Device

If you don’t have an OBD2 scanner right now, you can still keep an eye on your car and potentially diagnose any problems with it.

Your car will probably make sounds, emit odors, and/or feel a bit different to drive if it’s got a problem. Here are some things to keep an eye out for so that you can nip any problems in the bud.



One of the most obvious signs that there’s something wrong with your car is if there are leaks in the area in which you park it. So, always check that area when you move your car.

Dark liquid is especially concerning because it could be that the car’s oil is leaking, such as if your oil pan gasket needs to be replaced. Another common cause for leaks is a seal that needs replacing.

It’s also worth noting that if the fluid that’s leaking out of your car’s engine is red in color, this points to a problem with the transmission or power steering.


If you hear any strange sounds when driving your car, they should get your attention. Here are some sounds to keep an ear out for:

  • Grinding: This could be a sign that your clutch needs to be replaced or fixed, but grinding noises can also be a red flag for transmission problems.
  • Clunking: A clunking sound when you press the brakes can point to a problem with the brake discs experiencing wear and tear.
  • Screeching: If you hear a high-pitched screeching or squeaking noise when you accelerate your car, this can be a result of a worn fan belt that either needs to be tightened or replaced.
  • Tapping: A tapping noise that’s coming from underneath the bonnet can signal that the engine needs to be refilled with oil.
  • Loud bang: If this sound is coming from the back of your car, your car is backfiring. This can happen as a result of the mixture of air and fuel being too rich but it could also be a sign that the catalytic converter isn’t working in the way that it should. 



Sometimes your car could release some unpleasant or strange odors. Being aware of these and knowing what they mean can go a long way to diagnosing your car. 

  • Rotten Egg: This terrible smell can be a sign that your car’s catalytic converter isn’t processing hydrogen sulfide in the exhaust in the way it should. Don’t ignore this smell – take your car to your mechanic right away.
  • Syrup: If you smell something really sweet, almost like syrup, the engine coolant could be leaking. If you notice that the smell is even stronger inside the car, then you might have a problem with the heater core.
  • Burnt Paper: Ever smelled burned paper in your car? This could happen as a result of the clutch face burning as the clutch slips. If you’re always pressing the clutch when you drive, it can cause too much friction that produces heat which burns the paper-based clutch facings. Try to get out of this habit because it can result in the clutch failing.
  • Burnt Oil: This smell is usually a sign that you haven’t put enough engine oil in your car, so the first thing to do is check the oil dipstick and top up your car’s oil if necessary. Other reasons for this smell are that your engine is overheating or your transmission fluid is too low so the gears aren’t being lubricated enough.
  • Mustiness: If you smell something musty when you use your car’s air conditioner or heater, then this could be a sign that you have mildew inside the air conditioner evaporator. Turn off your AC immediately and drive with your fan on high so that the system can dry out.

Other Things To Notice When Driving Your Car 

Other Things To Notice When Driving Your Car

Smells and sounds aside, your car could give you a hint that something’s wrong in the way that it operates. Here are some things to look out for when driving:

  • Shaking or vibrations: If these happen, the problem could be a variety of issues that you should check. For starters, it helps to check that your tires and wheels are balanced and aligned. Other problems include a malfunctioning suspension and warped brake rotors, but these will usually cause shaking when you press the brake pedal. If you have a problem with your engine timing, this can also cause jerkiness and shaking. 
  • Pulling: If your car pulls to the side it can be scary, especially when you’re in the middle of traffic. Usually, pulling can be a result of steering, tire, wheel, or suspension problems. If your shock absorbers are malfunctioning, you’ll likely feel that yours is tilted and off-balance, and driving the car will be rough. 
  • Hard steering: If it suddenly feels more difficult to turn the steering wheel, you could be dealing with a power steering system problem in the belt, pump, or power steering fluid.
  • Loose brakes: If your brakes feel soft, this could be as a result of air being present in the brake lines or brake fluid that’s not at the correct level. If the brake fluid is old, this can start to absorb moisture and it doesn’t give you enough hydraulic pressure so that the brakes feel firm. 

Do You Need A Mechanic?

Do You Need A Mechanic?

If you know your way around cars, you might be able to fix some of the problems you’ve diagnosed yourself. But if you’re unsure of what could be the problem, then you’ll need a mechanic.

The same goes for if you know what’s wrong with your car but are unsure of how to fix it.

It’s also worth bearing in mind that there are some problems you shouldn’t try to fix yourself, as this could just cause more problems.

Examples of issues to consult a mechanic about include transmission problems, timing belt replacement problems, and car overheating problems.

If your car’s overheating, there’s a lot of risks involved with tinkering with it so you need a professional to diagnose the issue and do damage control on your car’s engine.

Related Questions

Can you get a free diagnostic test on your car?


Some auto repair shops can give you tests for free, while others will charge for diagnostic services.

Should you keep your old car?

If you maintain and repair your car when required, it can last you more than 200,000 miles! Bear in mind it’s usually cheaper to keep your current car than to buy a new one.


You want to keep your car in good condition, so it’s essential to pay attention to signs that something’s wrong with it.

Besides getting an OBD2 scanner that can help you diagnose your car’s problems, it’s vital to keep your eyes and ears peeled for any signs that something’s not working in the way it should.

If you’ve ever wondered, “How can I diagnose my car of problems?” now you have a better idea.


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