Media post: Using Automotive Code Scanners

You probably know that when the Check Engine Light (CEL) illuminates on your car, you should bring the car it to a mechanic to see what’s wrong. When you do this, the first thing the mechanic does is plug in a code scanner to “read the codes”. Basically what a code scanner does is interface with a car’s Powertrain Control Module (PCM) where all the engine error codes are stored. This allows them to professionally diagnose the problem and solve it. The service manager at Bosak Honda in Michigan City, IN, Michigans #1 Honda Dealer, says cars have been made with OBDII ports that allow scanning PCM modules since 1995.

This is how code scanners work: the fuel injection, ignition system and automatic transmission on most modern cars and trucks are run by the PCM. This computer collects operating data from the engine and other systems on the car and then send commands to the ignition coils, fuel injectors and other systems. They also store some of this operating data in memory so that mechanics can get insight into what’s been going on when service is needed.

When the CEL light on your car’s instrument panel goes on, it means that the PCM is receiving data from a sensor that indicates something isn’t working right. The PCM translates that sensor problem into a diagnostic code so a service technician can read it and know where to look for the problem. Sometimes some interpretation is involved when reading error codes but professional mechanics know most of the tricks.

Not long ago code scanners were expensive as they were really just for professional service technicians. Today, prices vary from $30 or so for a simple code reader to maybe $200 for full-featured machine. The inexpensive ones lack the fancy features of the high-end ones but they are quite useful, nonetheless. If you enjoy understanding what’s going on deep down in your car, consider getting one. They are available at all auto parts stores these days, and online at a multitude of websites.

Using a code scan tool is simple. To get started, plug the scan tool into the OBD II connector under the dash of your car. (If you can’t find the connector, check your owner’s manual. You may find a website or forum that can help you too.) After you get it connected, turn the car’s key on then follow the scan tool’s onscreen instructions. Eventually you’ll get an option to check for trouble codes and you will press a button to get them. You may want to write then down if you see any.

For interpretation, the manual that came with the scan tool may help, or go online. For most people, going on line is the best way to find out what the problem is. For example, on Google or another search engine, type in the model of your car and then the code number that the scan tool displayed. You will find dozens of sites that can help you diagnose what the problem is. Keep in mind that most of the responses you see will be non-professionals discussing the error code but usually, the solution will be identified by some of the more knowledgeable amateur mechanics on-line. Your ultimate resource is to have your local dealer take a look.