Service engine light on? (Don't spend unecessary money)

The (Service engine soon) or (check engine) light in your vehicle is intended to alert drivers of an emission control problem. This system is monitored by a computer in your car called an ECM (electronic control module). This is the brain of the car that receives all measured parameters of a running vehicle and adjusts engine performance accordingly.

99% of the time a vehicle's (check engine light) or (service engine light) is caused by a common problem. This problem normally occurs when people are in a rush or are simply distracted at the pump when refueling and forget to fully tighten the fuel cap. The fix can be as simple as re tightening the cap, until several clicks are heard, and allowing some driving time to pass in order for your engine light to reset. Your engine light will reset once certain checks have been completed on your fuel/emission system and your vehicle's computer realizes the problem has been fixed.

This simple fix is worth trying before taking the vehicle in for service, even if its a new vehicle. If after trying this your service engine light goes off and returns then most likely you have another problem besides a leaky fuel cap allowing gas vapors to escape from the tank. It may also be that you simply over serviced your tank with fuel and the fuel is entering your evaporator system which is intended to purge gases from your tank. If neither of these simple problems were the cause then you have a problem that will cost you some time and money to repair. These problems may range from a pin hole in your evaporator system causing a leak, a battery or alternator output problem, a faulty fuel system component, a faulty oxygen sensor, or any engine problems picked up by sensors monitoring your engines performance and emission control system. The later would be preferable because almost all vehicles including old have long lasting warranties on emission controls through its original factory warranty. I'm talking about 7 years average depending on vehicle manufacturer.

Regardless of what the problem may be, trying the above simple fixes will eliminate the gas cap and give your mechanic a reason to take a closer look. It may also save you valuable time and money spent at the repair shop just to find out it may very well have been operator
mal-function. That's a little embarrassing to me. Well not as much as driving around with my fuel cap completely off.

For the more persistent mechanically inclined person another avenue you can take to save money in trouble shooting this problem is to first buy a repair manual for your vehicle's make and model. Then go to your local automotive parts store, such as Discount Auto Parts, and for a small refundable deposit or maybe leaving your I.D with no deposit you should be able to borrow, free of charge, an OBD II, which is an On Board System Diagnostic Scan Tool.
This tool should be plugged in to a connector usually below the drivers side dash (If not found look in the repair manual for location) and with the ignition switch rotated to acc the position just before the cranking position you can begin a scan test on your vehicle. When ready the OBD II will prompted you what to do and give you a caution about the position of the ignition switch. Answer the questions on the testers screen by entering yes or no. If memory recalls the tester will ask if you are ready to run a test answer yes or run and Waite for the results. The results will be a code number followed by a short description. It will also state whether the code is pending or not. Pending means the ECU Electronic Control Unit or brain of the car has not yet finished testing the parameters of that particular system. write down the codes that are not pending meaning the ones that have failed.Look up the meaning of this code in your repair manual, OBD II CD Rom if new, or on line on the many useful sites providing codes. The repair manual should give you an idea were to start looking on your vehicle for the problem related to this code.

Note: This may not be a simple find because many times the problem is underlying within a certain system. Most problems relating to the light are not a part that has failed but what system is being affected by the failed part. On the other hand Some problems may turns out to be just a broken wire or an electrical plug that someone had disconnected and forgot to reconnect. This has happen to me with a map sensor which needed to be disconnected in order to perform preventative maintenance on the engine. Yes! even your mechanic can make a mistake. Some codes may be as simple as (map sensor) which you could then find its location in the manual and check out with an ohm meter to isolate the problem. But some may be a little more bewildering as (Bank sensor 1 circuit slow) this one may be pointing out an oxygen sensor that has gone bad, but you will not know for sure until you have isolated the problem, replaced the defective component and given the computer time to monitor the systems after a reset.

It may very well be that the engine light may return with the same fault code after thinking you have fixed the problem with a costly item. For this reason it is important that you follow procedures step by step in trouble shooting the faulty system. The codes may be cleared with a touch of a button (clear) on your OBDII Tester. Once cleared it will take a few trips at different driving conditions before your vehicle's computer is ready to monitor again. This may take days or weeks since it is not normally part of your daily commute.

For general information most vehicle's (check engine) light may also be reset by disconnecting the positive lead of the cars battery and reconnecting it after 2 seconds. To verify whether the system has been reset start your car and see if the check engine light stays illuminated. If it goes out the system is reset and as mentioned above will take a while to be ready to monitor again. Important: if your vehicle is equipped with an anti-theft radio and you disconnect the battery, which eventually you will in the event of replacing a dead battery, be sure you know your radio's code. The theft feature is active if the red light by the radio is flashing.
Be warned:If you don't know the code, your radio will not allow you to control it until the proper code has been entered. You can enter a new code (change the code) only when the radio is in a controllable state, by following instructions in your owners manual for this task.
Good luck, hope this information was use full!