Diagnostic OBD Scan Tool is Not a Magic Wand

Did you know there are situations in which a diagnostic OBD scan tool might not be enough to track down the issue? Although some of them come with various advanced options, even the most powerful ones can have trouble finding the source of the problem. Just like with many other things in life, any diagnostic tool is only as good as the person using it. To use all available features of any diagnostic equipment, the operator must have a certain level of automotive knowledge both technical and practical. 

In this article, we will see what are the limiting factors when using OBD diagnostic scan tools and how to overcome them.

Can I rely on diagnostic trouble codes alone?

While the car is running, the electronic control unit monitors a range of data coming from various sensors. Based on this vital information, the ECU continuously adjusts engine parameters to ensure better fuel economy and improve overall performance. If any of these values goes out of predetermined range, the driver will be warned by a ‘check engine’ light. In addition, the ECU will store a diagnostic trouble code inside vehicles fault memory. This is a specific set of information that is very helpful during troubleshooting and repair processes.

To access diagnostic codes and get an insight into the running parameters of your car, you will need a suitable OBD Scan tool. There are different types of OBD scanners available on the market, ranging from simple engine code readers to complex and powerful diagnostic equipment with ECU coding capability. Despite their differences in abilities and prices, all of them offer a simple way of reading and clearing stored trouble codes triggered from the engine/emission system. This makes the troubleshooting process quite straightforward and far more easier, or this is how it should be in the perfect world.

However, there are many real-life situations where relying only on error codes can be inaccurate and misleading. This is because the ECU decides on running parameters and potential error codes based on the reading from sensors. If there are disturbances in this communication, the ECU may interpret it as a faulty sensor and store a corresponding code. However, instead of the sensor itself, the cause of the problem might be damaged wiring or a loose connector. By relying on the code and without performing additional tests, you might end up with a wrong diagnosis. Besides unnecessary costs, this also causes prolonged vehicle downtimes as it takes more time to fix it. The best way of avoiding this is by double checking the suspected component, together with connecting parts and wirings.

How can various diagnostic data and features help me pinpoint the issue?

In order to meet strickening demands on emission control and overall performance, modern cars use a range of advanced technologies. Although this improves the driving experience in general, the resulting complexity increases failure chances and makes troubleshooting more challenging. Because of the overlap in functions of various systems, failure within different components can cause an identical error code. In addition, with less apparent issues that will not trigger a check engine light, there will be no trouble codes. In most cases, tracking down the source of problems like those require a methodical approach and an in-depth investigation.

All scan and diagnostic tools offer various additional features, depending on their level of complexity and built-in capabilities. Using them to obtain and analyse various values gives you a better insight into the problem and helps eliminate potential causes. One of the most useful features is live data, which taps directly into the feed between the ECU and sensors. This will allow you to see various vital values in real time and spot any potential anomalies. Most scan tools will allow you to keep track of different crucial parameters, like engine temperature, speed or load. This is helpful when you are dealing with issues that only happen under certain conditions. Powerful diagnostic tools go even further, as they come with the ability to adjust or activate and deactivate various systems. Skilled operators will use these features to track down sources of unusual sounds or to tune components for optimal efficiency.

Still, the biggest obstacle that both amateur and professional users usually face is the lack of knowledge and experience. Features like live data streams give a clear overview of engine running parameters. Still, it is up to you to decide which of them are important and recognise any irregularities.


As we have explained here, scan and diagnostic tools will give you an insight into running parameters of your engine. Even the less expensive ones can access things like trouble codes or live data, which is enough for amateur users. More powerful diagnostic tools, aimed at experts, offer a range of additional features that ease the troubleshooting process. However, the end result will depend on users' knowledge and experience, as professional judgement plays a significant role here.