2002 Cadillac Deville SERVICES ENGINE SOON LIGHT STAYS ON

You need to stop by a parts store and have the codes read because the engine light comes on when there has been something cause it to come on autozone will check it for you for free and almost any other auto store will do the same also most auto shops will also and they will let you know the reason it came on

You will need to have the computer scanned to find out what has triggered the light, You can clear the computer memory but, if it is a component failure, the light will right back on again.

That would be the O2 sensor bank one here is a diagram showing were it is on your car the left side of engine it would be the one closest to the engine you have to lift car support with jack stands spray wd-40 on sensor let sit for about 5 min. unplug and remove sensor and install and plug back in and to turn off engine light you will have to buy a code reader or go to a shop you know well and they can turn light off you can buy cheep code readers for about $50.00