How To Troubleshoot Car Problems at Home in 5 Steps

car troubleshooting

Does your mechanic constantly replace the wrong parts and you just pay whatever he says?

That’s because they didn’t do a good job of troubleshooting and they make more money if they can replace more parts as long as you just pay them. This is a very common problem because many customers don’t ask or don’t understand what your mechanic is doing in your car.

In this guide, I will explain how you can do much of the troubleshooting yourself with some cheap tools you may have at home.

How To Troubleshoot Car Problems

1. Read the DTC trouble code memory

troubleshoot car problems

In almost every troubleshooting session I do, which is related to an electrical or motor part, I start the troubleshooting by reading the DTC error code memory. Today’s cars are really intelligent and can detect problems really well. When one of the ECUs sees a problem, it stores the fault directly in the error code memory. So you should always start by reading the errors.

The error codes are stored in the memory for a very long time and every time you start your car. This process is called a “cycle” and the vehicle tests the error every time you start a cycle. A lot depends on what type of car and ECU it is, but most cars will try the problem about 20-30 times. If the ECU can’t find the problem 20-30 times, it will automatically clear the error code.

If the ECU sees the problem once between the 20-30 cycles, it starts over again, so you have a really good chance of seeing the error code if you use a diagnostic tool.

Many garages use very expensive diagnostic tools and therefore you have to pay a lot of money even if the fault memory search only takes 10 minutes. But in many cases, these expensive diagnostic tools are not necessary.

If you want to read the memory in the engine control unit, a cheap tool will work almost as well. The cheap tools might find it a bit more difficult to search for all other ECUs, but in some cars, the cheap tools can do the same job. Always read the description of the product to see which cars it works on before you buy it.

Instead of paying the garage more than $100 every time they want to check the engine’s DTC memory, you could buy a diagnostic tool for under $70 and do as many DTC memory searches as you like.

If you are considering buying a diagnostic tool to have at home, there are a lot of different tools available. One tool I can recommend is the ANCEL AD410 Enhanced OBD2 Vehicle Code Reader. You get a really good tool for a small amount of money. It can read and erase the DTC memory of most vehicles on the market.

If you get an error code from the memory, you can read the error code number etc. P0301. Once you’ve received the full name of the error code, you can either use Google or ask us and we’ll give you information about what the error code is and what the possible causes might be.

Check out if you can find your trouble code here:
Generic DTC codes

2. Find information about the trouble code

car troubleshooting problems

The next step is to find as much information as possible about the problem. You need to research and get the right information. What exactly does the error code tell us? What are the possible causes and what are the reasons that the ECU would store this error code? You can never get too much information about the error code.

Many people and even mechanics only read the first words of the error code and then go to the workshop as soon as possible and order the part they think. This can cost you a lot of unnecessary money, and just by looking for more information, you could use that money for something nicer.

Searching for information on the Internet is free and can be done by anyone. So why hurry so much to order a part that has a 10% chance of fixing the problem? I will show you a good example of what I am talking about.

You read the DTC trouble code memory and you see this trouble code:

P0341 Camshaft Position Sensor Circuit Range/Performance

Many people are just seeing the words “Camshaft Position Sensor” and then ordering a camshaft position sensor.

Now take a look at this trouble code:

P0340 Camshaft Position Sensor Circuit Malfunction

It’s the same error code, isn’t it? No, these error codes are completely different from each other.

The first error code says that the camshaft position is wrong; it could be a faulty camshaft position sensor, but the probability is very small. You probably have a problem with the camshaft alignment or the timing belt. What do you think will happen if you replace the camshaft position sensor and continue driving after that? Yes, if it is a problem with the timing belt, not only are you wasting your money on a new sensor, you may even destroy your entire engine.

The other code tells us that there is an electrical problem with the sensor or the wiring to the sensor. With this information, we know that we don’t have to start checking the camshaft control first. I hope you understand what I’m trying to say.  This is why it is so important to find the right information and see what the error code says; it could save you a lot of money and time-consuming work.

If you can’t find good information on the internet, you can ask us on this website. Send us a question and write down the error code number you get, etc. P0340 and write the car model and engine.

3. Find similar cases

car troubleshooting problem

Many of the problems with cars are general problems. Since engine models are built the same, you are probably not the first person with the same problem. Finding cases where the problem has been solved before could save you a lot of time and money. You may not always find exactly the same case, but if you find similar cases, you might at least get an indication of where to start troubleshooting. You can either search the internet or check our database to see if we have ever had similar cases answered before. If you can’t find information about similar cases, you can send a question with as much information about your error as possible, and we can check if we can find any similar issues.

In some cases, you may not find other similar cases, and then you have to figure out how to figure things out for yourself. I will explain how to do that in the next step.

4. Get wiring diagrams/other information

troubleshoot car problems

Now that you know what the error code tells you, and you may have found a similar error, it’s time to make sure you replace the correct part. Just guessing could be expensive, and it costs nothing to do a good search. Again, before you pick up your multimeter and start just measuring parts, you need to know how the parts work and what test results you should have.

If you have a part that you suspect, you need to find information about that part. Find information about measuring it or test it to make sure you have found the faulty part. Sometimes it can be very difficult to get accurate readings when troubleshooting. Finding good information that you can trust can be difficult. But we are lucky to have internet, and there are many sites that offer the original repair manuals for free. Just find out the engine code for your engine and car model and search for this and the repair service manual and you will get many hits.

Repair manuals often contain a lot of good information on how to measure or test the parts and what they should be like if they are OK. It can be a bit difficult to find the information you are looking for, but once you have learned how they work, it will not be a problem. Troubleshoot any parts that you think might be faulty several times to get a result you can trust, and once you have found it, look for the part number you are looking for to get the right parts.

If you are looking for cheap parts for your car, I can recommend that you look on eBay. There you can find a lot of both new and used parts at a good price.

If you think you’ve found the problem and received your parts, it’s time to move on to the next step.

5. Repair the problem and try it out

troubleshooting car problems

You can look again in your repair service manual to make sure that you do a proper and good job when replacing parts. This will greatly facilitate the entire troubleshooting process. Once you have replaced or repaired the correct part, it is time to take a test drive to make sure the problem has disappeared. First, before you take your vehicle for a test drive. You must ensure that you have cleared the DTC’s fault code memory! Clearing the fault memory after you have made a repair is always a good idea, both for you and perhaps for the next owner, because I told you that fault codes can be stored in the memory for a long time.

If you don’t clear the memory before that, you might fool yourself by taking a long test drive and, after everything has worked properly, checking the fault memory and still getting the same fault code stored. Make sure you clear the error code memory before taking a very long test drive. Try out all possible scenarios on the road where the fault could occur, such as many different speeds and extreme situations.

I recommend that you drive a few miles, park the car at the side of the road and switch it off, remove the key and start the car again. That’s because of what I explained to you earlier. The ECUs work cyclically and some error codes are not registered until they detect the problem in 5 to 10 cycles. Therefore, it can sometimes happen that a very long test drive does not allow the error to occur.

If you have tested the car in many cycles and you think the problem is OK, then it is time to check all the error memories again to make sure it is clean. If it is clean, then you have been successful with the troubleshooting and probably saved a lot of money!


  • It’s always good to take some time and do some good troubleshooting to avoid throwing your money away.
  • Find as much information as possible about the error codes and repair information. This will save you a lot of money in the end.
  • Instead of wasting $100 every time your workshop searches your fault code memory, you could do the same job with a cheaper tool you can have at home.
  • Always start troubleshooting by searching for error codes first.

I hope you have learned something in this guide and that your troubleshooting was successful. Now you can go to your workshop and tell them how to do a proper troubleshooting! But at least I hope that you will save a lot of money by doing the troubleshooting yourself at home. It’s always fun to teach people how to do it yourself instead of just giving the work away to someone who probably isn’t very careful with their money and just guessing what’s wrong.

If you have any questions or need further help with troubleshooting, you can contact us here on this page to ask your questions. I’d really like to hear what you think of this article, and if you want us to add or edit anything, you can leave a comment below here. I would really appreciate it!

See you in the next article and don’t forget to read our other articles if you want to know more!

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.