Vehicle Diagnostic Tools For DIY Use

Vehicle Diagnostic Tools For DIY

Trying to figure out the issue from the persistent “Check engine light” to the battery warning light, diagnostic tools have made our lives tremendously simpler by taking out the hassle of trying to figure out what’s causing the problems in our vehicles. 

In the past, mechanics had to rely on their senses and a few basic hand tools, to painstakingly find the problems in the vehicle. But modern vehicles have gotten more technologically advanced, and the use of electrical and electronic systems and devices has drastically increased. This makes it possible to easily find and fix faults in the vehicle using just the right equipment. 

In this article:

What is a Diagnostic Tool?

Diagnostic tools are used to find faults or defects in a system most commonly using an electronic signal. When you hear car diagnostics tools, the first thing that springs to mind is OBD or On-Board Diagnostic tools, but in reality, even a simple multimeter is a sort of diagnostic tool that helps out most technicians in several ways. Diagnostic tools are essentially electronic devices that can process electronic signals which allow the user to get appropriate data useful in that scenario. 

Keep in mind that this does not mean a multimeter can perform as an OBD tool since these are primarily designed to read engine trouble codes whereas, a multimeter is an electronic measuring instrument able to read voltage, current, and resistance. 

What are the Diagnostic tools used on cars?

In this section, we will be covering all the different vehicle analysis and diagnostic tools that come in handy to even the most basic DIYer looking to solve various issues on his/her vehicle.  Here are some of the most commonly used car diagnostic tools:

OBD Code Readers And Scan Tools

Since the inception of the OBD II system in 1996, every new vehicle has had a standard onboard diagnostic system that stores information in the vehicle’s electronic control module. This information is then used to access trouble codes from the engine, transmission, exhaust, and various other systems in the car. A code reader or scan tool reads and displays the related engine trouble code. Every system in the car has a different trouble code and this allows the technician to pinpoint the specific area of the problem using the related engine code. 

There are several types of code readers and scan tools available on the market today with varying prices and capabilities. The cheapest of the bunch is simply able to read the OBD system and spew out all engine codes related to the fault. The codes alone can not be enough to find a fix and you may have to further investigate the codes by looking them up online. Scan tools are more advanced and along with reading and displaying the engine codes, this device is also able to give solutions and reasons for the issue to occur. This information can be helpful as it allows the user to solve the issue more efficiently. Professional OBD scan tools are generally only used by dealerships and manufacturers as they are more advanced and have features like ECU reprogramming, emission control, etc that are not directly relevant to the average DIYer. 

Code readers and scan tools have become increasingly popular as they are a relevant and easy source of finding and fixing common problems associated with most vehicles and using one are very simple. It is useful to note that these tools are not magical devices capable of solving all vehicle-related problems. Instead, they make it easy to solve the issues by helping you isolate the faulty system in the engine and various other components. 


There are numerous electrical components and circuits in a car that can go wrong due to several reasons like broken wires, dead fuses, water damage, etc. these issues can always be extremely hard to locate mainly due to the number of wires a car has. A multimeter is a helpful tool to determine electrical issues in the system. A multimeter is a useful addition to every DIYer and mechanics toolset. 

Circuit Tester

If you find the multimeter very complex to use and understand then a simpler alternative for you is a circuit tester. These devices lack the capabilities of a multimeter but are useful to easily find a broken circuit or faults in the circuit like torn wires or altered connection. 

Battery Tester

The battery is one of the most important elements of the vehicle and also one of the most prone to regular breakdown. It can be hard to know why a brand new battery is acting out and not working properly. This is why a battery tester is a useful and inexpensive tool that can not only analyze the battery but some testers can even test the vehicle charging system operations. Battery testers typically show the battery voltage, its charge holding capabilities, and its health or how long it can last before requiring a replacement. The charging system can also be tested which can tell whether the issue is related to the alternator or the battery. 

Inspection Tools

When it comes to diagnostic tools, one of the most useful devices is an inspection camera. They can be especially useful if the faults lie in areas where you cannot easily see or perhaps in an enclosed section like the cylinder combustion chamber inside the engine. Inspection cameras provide an insight into areas and sections of the engine which would not be possible without complete dismantling of parts. This allows the mechanic to determine problems like carbon buildup on cylinder walls and valves, broken crankshaft bearing, damaged piston walls, etc. which would not show up on any electronic scan tools but can only be determined using good ol’ fashioned prying. 

Similarly, a mechanic’s stethoscope is a device that enhances any sounds or disturbances to diagnose failure issues with many engine components like bearings, water pumps, injectors, etc. The stethoscope allows the user to listen to the harmonics being produced which is used to find issues and help figure out the problem-causing part.  For example, a broken bearing will sound particularly rattly or create grinding noises that would not be apparent without the use of a hearing aid. 

Inspection tools are straightforward to use and depend entirely on the user's knowledge and investigative skills; however, it is fairly simple to distinguish a broken part from a functional one. If you regularly work on the engine, transmission, or any hard-to-reach places and require sophisticated snooping, then inspection tools are your best bet. 

Spark Tester

Another useful tool to diagnose ignition systems or spark plug problems is a simple and ingenious spark tester. If you suspect that one of your engine cylinders isn't functioning then start by assessing if the spark plug is working which can be done with the help of a spark tester. Remove the HT (high tension) lead running to the spark plug and attach the tester in its place. The tester boot attaches to the spark plug end and the tester prong connects to the HT lead. Now start the engine and look for the tester light. If it illuminates then move on to the next spark plug and test again. If the light doesn't go on then you know the issue is related to the ignition system.

Compression Testers

Engine issues are by far the hardest to diagnose simply because of the extent of its components and various working parts. A compression tester helps narrow down the search by letting you know if a particular cylinder is causing the issue or not. These testers check the compression created by each engine cylinder and help isolate the issue to the faulty one. If you are not able to solve the problem yourself, it will still give your mechanic a head start. 

No matter what the trouble is, there are always tools that can help you find and even fix the issue. While increasing your knowledge and aptitude for the parts in your car, these tools also make you more aware of what could potentially go wrong that you could fix before it turns into a major problem requiring more expensive fixes. Diagnostic tools are a definitive part of every technician's toolbox and a very useful addition to those who love working on their cars. Being able to diagnose and fix problems yourself will save you plenty in mechanic’s bills. And even if you are not able to fix the issue yourself, you can direct your mechanic to the problem beforehand, saving yourself time and money. 

John Framigllia
Technical Writer
Our technical writer is known for simplifying automotive parts and services. Intuitive with various vehicles and manufacturers, he knows how to simplify complicated problems.