Unable to Read Your OBD-II Codes?

Try This Simple Check Before You Freak

Troubleshooting Engine Codes
The laptop can detect problems and diagnose OBD Codes. Getty

If you are scanning your car's computer for OBD Codes and getting nothing at all, there are some things you should check before you give up and take your car to the shop. If you are resourceful enough to utilize your car's On Board Diagnostic (OBD) system, you're way ahead of the game. If you can't remember what an OBD-II Code even is, let me give you a quick refresher course on diagnostics, error codes, scan ports and such.

Since the mid-1990s vehicles have had a built in troubleshooting system known as On Board Diagnostics. There is a computer in your car someplace that monitors a bunch of sensors. These sensors measure things like engine temperature, exhaust gas mixture and many other metrics that would mean very little to the common person without the help of a serious troubleshooters mind, or the Internet! The computer in your car or truck is constantly monitoring all of these sensors to be sure they are all reading in what the manufacturer has decided is the optimum or safe range. If they go out of the range, the computer makes a note of it and stores this as an Error Code. In a modern car, there can be hundreds of error codes, but each of them points to a specific issue. As a mechanic -- professional or do it yourself -- these codes can be accessed in order to measure the overall health of the engine.

You do this by plugging a scan tool into a computer style port on your car (your repair manual will show you where it is) and downloading the codes. Then you can go to a site like OBD-Codes.com and see what the codes translate to. 

Don't forget you can have your codes scanned free at most auto parts chain stores.

If you've plugged into your car's diagnostic port and aren't reading anything at all, you might think that your OBD-II brain has fried, but don't declare it dead yet.

If you're getting nothing, check the fuse!

On many cars, the ECM (that's the electronic brain or computer) is on the same fuse circuit as other electrics like the cigarette lighter / accessory port. The lighter is prone to blow fuses on some vehicles, and if there's no juice going to the ECM, it can't tell you what's wrong. Even a fuse that is dedicated to the car's computer diagnostics can blow for no apparent reason. The biggest cause for getting no OBD code at all is a blown fuse. Check your fuses to be sure none of them have gone bad. Keep in mind, too, that your car or truck may have more than one fuse box. This should be covered in your owner's manual or a proper service manual.

From time to time, the scan port can become clogged with dust from years of being unused. You would never want to spray a cleaner or get the port wet, but wiping it with a soft cloth or blowing some compressed air across it can help clear out anything that may be preventing your scan tool from getting a good reading. Now that you know what codes your vehicle is storing, you can get going with some regular vehicle maintenance!