What to do when the Check Engine Light is on
The "check engine" light, also referred to as a malfunction indicator light (MIL) doesn't always mean that there is a serious problem. It is always seen, but not always understood.
This system, the MIL system, is monitored by a computer, rather than an individual circuit, so the cause is not always known. This one system monitors items from Engine Management, Emissions all the way to Accessories. The only way that you can truly know why this light comes on is to have your vehicle connected to an OBD II (On-board diagnostic) scan tool. This scanner is connected to a terminal that is underneath the steering wheel, allowing it to pick up the codes that the computer is relaying for this light to come on. Some of the codes that are given will either give a general idea of where the issue is or an exact problem.
Once this code is received, you know where the problem exists, making repair much easier rather than just wondering why. Without it, there is no way of really knowing why it is on, unless you are a mechanic with the complete know how to diagnose a issue.
Everything from not making sure your gas cap clicks three times to something such as the Idle Air Control Valve can make this light come on. The first thing that you should always do when this light comes on is to make sure that gas cap is on tight. The last thing you want to do is get all worried because the light came on when it was such an easy fix.
Other main causes for this light to come on are the Intake Air Temperature, Oxygen Sensor and Manifold Pressure. Most of these things aren't ones that we want to try and take care of ourselves, especially if we don't know how to. There are qualified mechanics out there that can get you "up and running" in no time.
However, we all need to remember that even if this light does come on, doesn't mean our car isn't running right or efficiently. The oxygen sensor, which is a frequent reason why this light comes on, will not affect your vehicle or the way it drives. The most that one would see from an issue such as this is a weird smell. Don't feel that you need to run straight to a mechanic to get the light to turn off right away. Most of the time, it won't hurt anything if you wait a week, sometimes even a month. However, if you do notice that there are issues with how your vehicle functions, make an appointment at your earliest.
Many states now require that this light not be illuminated in order for you to receive your safety inspection. Make sure that after you leave the repair shop that this light does not come back on within a few days. A vehicles check engine light can be made to turn off, even if it isn't repaired. The OBDII Scan Tool is equipped with the option to "clear" codes. So even if the problem is addressed, this code still has to be cleared by the mechanic. It won't turn off on it's own, even if fixed. Vehicles have a memory just as a personal computer does. The vehicles system needs to recycle for its computer to understand that the issue has been resolved.
If the "check engine" light comes back on, this will mean that the issue was never properly fixed or there is an additional issue. If this happens, always return to repair shop that initially fixed it, because if it was caused by something they did, they have to fix it
Before allowing a mechanic to repair your vehicle, make sure that the warranty does allow for him to do so. Not heeding the warnings on a warranty may void it, leaving you without it when it may count.
