What causes the service engine soon light to come on

It would be kind-of nice to know what kind of vehicle we are talking about. It would also be nice to know WHAT ABOUT O2 sensor??? If the engine is misfiring, there are several things that can cause this. It could be anthing from a worn out spark plug, all the way to a cracked cylinder head and a whole bunch of other stuff in-between. The problem must be DIAGNOSED. The service engine soon light is trying to tell you that there is a problem and that you need to get your engine control system serviced! If the engine is misfiring, the Service Engine Soon light is SUPPOSED to be on!

There are really too many things to list that can cause the service engine soon light to come on. I suggest you have your mechanic scan your vehicle to see what codes are present to cause the light to come on.

The information below was complied by me, it explains what causes the check engine light or Service Engine Soon light to come on and the process of finding the cause.

When the Check Engine light or Service Engine Soon light (depends on make) is turned on the computer control unit (called the PCM) has sensed a fault in the electronic controls of the engine and/or the emission system. When this happens you will seldom feel the car engine run any different. There are about 200 possible faults that turn the Check Engine light on, to know what has developed a problem you must have the system tested, this is called an OBD2 fault code test, Kragen and Autozone parts stores do this testing for free.

many things can cause the service light to come on, check the gas cap make sure it seals, otherwise get it scanned,.

Need to scan the car for codes that caused the service engine soon light to go on.

If it's the indicator that literally says "service engine soon", and not the check-engine light, then you have no worries. That's programmed to come on at set intervals to remind you that routine service may be due soon (oil change, inspection, tire rotation, etc). It's not an indication of failure. Failures will be shown by the check-engine light. That one is nothing to worry about. Your owner's manual should have a procedure to turn it off.

Need to have sombody with a scan tool scan your vehicle, which will give you a dtc (dianostic trouble code) and determine what is cause the service engine soon light to come on

replace the 02 sensor and the light will go off.

wandeeful: what has occurred, is something within the powertrain management system had malfunctioned. It may had occurred even for a brief moment. There will be a code stored in the computer which will tell what had tripped the light.
Once the scan is completed, then what need to be done will be known.
You can get the car scanned for free at
Auto Zone or "O" Reiley's

the problem could be that your car is missing ,and causing the light to come on for a miss code.