Any faulty engine sensor can cause this light to turn on as well as a bad fuel cap, one what wasn't tightened enough or a lost one. You will also find that a vacuum hose that has come loose will turn that light on. You can take your vehicle to an auto parts place such as advance or auto zone and they will check why that light came on hope this helps.
On a 2003 Lincoln Navigator : The check engine light / service engine soon light is a drawing of an engine located directly under the center of the tachometer
Auto Zone will check your engine codes for FREE. After finding out what cause your engine light to come on. Then the problem can be resolve with out guessing.
I would check your alternator*(check the spelling).
advance auto or OB II code reader
If the check engine light is on for a 95 Lincoln town car, check the computer codes. a problem could cause low fuel economy, or cause a part failure over time.
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
Check your manual.
Typically, you will use 5 quarts of oil. Check your manual for the correct oil capacity. ======================================================== According to the ( 2004 ) Lincoln Navigator Owner Guide : With engine oil filter change : ( 7.0 U.S. quarts / 6.6 liters of 5W-20 )
Check: NADA.com autortrader.com Kbb.com
Auto Zone will check your engine codes for FREE. This way you will know for sure what it is. It maybe a bad Oxygen Sensor.
If your refering to the engine light been on. Auto Zone will check the codes for FREE. If other lights then we need more details...
Check Owner's Manual. If you do not have one. Check Related links below.