Working with Scan Tools (OBD) and Other Diagnostic Equipment Explained

Car scanners are now more affordable than one visit to a dealership for diagnostics. You can buy cheaper ELM scanners starting at $15 or something. Of course, they aren't perfect and won't communicate with all possible electronic control modules, so they have very limited functionality. But still, they work.

In this article, I want to recap everything I and my colleagues wrote about scan tools and their use. I hope this helps you use them right. Of course, you need to know what exactly you want to get from a scan tool before you start using it in your car. This will help you choose the proper tool to buy or borrow.

Can you check fuel injectors with your scanner?

Checking fuel injectors with a scanner directly is impossible. But there are certain codes that may narrow down the possible range of problems and include in the list of possible culprits exactly the fuel injectors.

For example, the P0300 code (multiple cylinders misfiring) can show that several injectors may not be working properly. Or the P0302 code may show that the injector in cylinder 2 is faulty. Also, codes showing too lean or too rich a mixture may refer to bad injectors.

Checking injectors with the scanner highlights:

• Difficulty level:Medium
• Needed scan tools:Basic will do well
• Additional equipment:Tools for car repair
• Timeneeded:Several minutes
• Price in a shop:$150 - $250
• DIY repair:Possible but quite complicated

How to clear codes with a scan tool?

Clearing codes with a scan tool is possible in those cases only when you have the app or a more expensive scan tool that allows you to give certain commands to a car. A simple ELM scanner with no good app won't help you in clearing the codes.

Whenever you clean the error code, you should know that it may come back if the problem is not solved. You should check how long a certain code may be stored.

To do this, find the option in the menu of the app that says "Delete Codes" or "Clear All Codes". It's usually hidden in settings or there is a dedicated tab in the menu for clearing the errors.

Also, you may try doing this without a scanner if your car supports this in its menu. Alternatively, you may just disconnect the battery for some time and the generic codes will be cleared. If the codes come back, you need a more professional inspection and repair.

Clearing the DTCs highlights:

• Difficulty level:Low
• Needed scan tools:Professional tool or app
• Additional equipment:No other tools needed
• Timeneeded:10-15 minutes
• Price in a shop:$150 - $250
• DIY repair:Possible

What if there is a code but no check engine light?

It's quite possible that your vehicle has a trouble code (permanent code) in the ECU but no check engine light is illuminating on the dash. The problem is that the code may not be as important or it may hang there for months and be inactive. After clearing, this code may never come back. Or it may not affect the overall work of your car, so the check engine light won't turn on.

Code but no CEL highlights:

• Difficulty level:Medium
• Needed scan tools:Basic will do well
• Additional equipment:Good app will help
• Timeneeded:15-20 minutes
• Price in a shop:$150 - $250
• DIY repair:Depends on the code

Where to put car scanner in your car?

Every modern vehicle has the diagnostic slot which is, in 90% of cases, the OBD2 port. In several car brands, other slot types may be used. You should check this before you buy a certain type of scanner for your car.

This port may be located in various places. The most common ones are in the upper part of the footwell on the driver's side, in a special section on the lower side of the front panel, behind some plastic lid in the lower part of the central console, etc.

Scanner tool connection highlights:

• Difficulty level:Low
• Needed scan tools:Any scan tool
• Additional equipment:Driver's manual will help
• Timeneeded:1 minute
• Price in a shop:$150 - $250
• DIY repair:Possible

How to learn fault codes without a scanner?

If you don't have a scanner tool, you may try getting the codes without it. In BMW and Subaru cars this is sometimes possible. They will not show all the codes, but they may give you some hints on how you can start repairing your vehicle.

For this, you will need to learn how to use the settings in your car and browse different tabs in these settings. Of course, everything is described in the driver's manual. But I've also written an article to explain this.

Learning codes without scanners highlights:

• Difficulty level:Medium
• Needed scan tools:No tool needed
• Additional equipment:Driver's manual will help
• Timeneeded:20-30 minutes
• Price in a shop:$150 - $250
• DIY repair:Possible

Code for bad ECM

In most cases, the bad ECM will not throw any codes but will be heavily glitching making it impossible to drive your vehicle. One of the possible codes you can catch is the P0601 code which means that the ECM is getting low voltage or is malfunctioning.

Other than that, the faulty ECM may throw all kinds of different random codes which is misleading. You should notice that there is no consistency in the codes when the control module is in trouble.

Codes of the faulty ECM highlights:

• Difficulty level:High
• Needed scan tools:Professional scan tool
• Additional equipment:No other tools needed
• Timeneeded:20-30 minutes
• Price in a shop:$200 - $350
• DIY repair:Impossible

No fault codes stored in the ECU

When there are no codes in the ECU, it means that the electronic control module doesn't see any problems. Of course, it doesn't mean that your car is perfectly fine. The ECU is only responsible for a small part of your vehicle and there may be codes in other control modules that you can't read with a basic scan tool.

Also, a lot of ECU models aren't that smart to throw a code for every possible problem. Usually, the codes in the ECU are quite generic and give you little to no good info for further inspection.

No codes in the ECU highlights:

• Difficulty level:Medium
• Needed scan tools:Professional scan tool
• Additional equipment:Depends on the problem
• Timeneeded:20-30 minutes
• Price in a shop:$200 - $350
• DIY repair:Impossible