You’re tooling down the road; it’s a beautiful, sunny summer day and then it happens; You glance down at your instrument panel and the Check Engine Light (CEL) is glowing.  Great, you think; exactly what does this mean?  You might prefer to simply call Sheridan Nissan and have a mechanic look at it or perhaps do a little research yourself. In this article, we will look at automotive code reader tools and how you can get some insight into what’s going on behind the scenes when your CEL goes on.

First, some background: The fuel injection, ignition system and automatic transmission on most modern cars and trucks are run by computers. These computers collect operating data from the engine and other systems on the car and then send commands to the ignition coils and fuel injectors to fire the cylinders and then they fine-tune the combustion process with the correct amount of gasoline.

Sounds precise right? And it is–until there’s a malfunction. Often, your first indication of anything is that CEL is glowing on the dash. When that light is on, it means that the Powertrain Control Module (PCM) is seeing data from some sensor that indicates something is wrong. So the PCM guesses what should be a good default number to substitute for the sensor’s erratic output and the car continues running. The PCM also stores a diagnostic “trouble code” so a service technician has some clue where to look for the problem.

We chatted with Sheridan Nissan Used Automobiles and they said code scan tools are what both professionals and owners use to check these codes. Not long ago scanners were the province of professional technicians but now they are inexpensive enough for anyone to buy. Prices vary from $20 or so for a simple code reader to maybe $400 for full-featured, upgradable machines with computer interfaces and multiple languages.  Note that pro-grade scan tools have graphic functions that let a technician watch several parameters onscreen while the engine is running.  This sort of power really isn’t needed by consumers or even DIYers. Many car owners just opt for the cheaper units and then use the internet to find out what the codes mean.

How are they used? It’s simple, to get started, plug the scan tool into the OBD II connector under the dash.  (If you can’t find the connector, consult the internet.)  After you get it connected, turn the key on then follow the onscreen instructions. You’ll get an option to check for trouble codes, as well as a couple of other menu choices. When you read these codes, write them down before resetting the system.

For interpretation, you have the internet.  Just type in the model of your car and the code number and you will find dozens of sites and many discussions that can help you out.  Your ultimate resource, of course, is to have your local Nissan dealer take a look at your car though.  Give the folks at Sheridan a shout for further details.

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