2005 Cadillac Seville. Replace gas cap displayed and service engine soon lightcame on. Replaced gas cap however service engine soon light is still on and the car is due for smog. Help please

your serpentine belt needs to be replaced

i have got this code before and it just be lose gas cap.....but have also had to replace the cap on a few of them .....the vent hole in it gets cloged....hope it helps

The fact that the light came on has nothing to do with filling your tank. The light is pre-programmed to come on following a combination of time, mileage and on some makes the usage profile, and it's telling you to get the engine serviced soon. After the service, the vehicle will need to be connected to a suitably-equipped computer to have the service light indicator reset. If you check in your Cadillac owners' handbook, the service section will give you details of which service items need to be attended to at the age and mileage of your vehicle. If it's just a simple oil and filters service then you may decide that you can do this yourself easily and save money. If there's more to the job, you can decide what you're comfortable doing yourself and then get a garage to do the rest: the less you leave to the garage, the lower the bill.

Ignoring the light will simply mean that your engine eventually has a breakdown which can be extremely expensive.

replace sensor at gas fill up tube

To confirm whether or not this is from some drips at the gas pump, you can turn the car on and watch the cap. You may be able to observe it pushing out air. In this case you should replace the cap and/or clean any rust and dirt from the filler neck so it can seal properly.

there is a lose wire

what do you mean it , shows electrical?

The light on just means you are not passing emissions. not a big deal unless it's flashing.
Go to Autozone, they will scan test for codes for free.

put a new gas cap, those system are pres. even if
the cap look ok it maby leaking replace with a new
one it should solve your prob.
eng.ligh come on because of the gas cap

The light is on to alert U to the fact that a fault has occurred in the engine management system(s) or a part of the emission control system, there are over a 100 different problems that turn this light on, take the car to any Kragen auto parts,Auto Zone, Shukes etc and they will test the system for free, it could be as simple as a loose or defective gas cap seal, no way to tell until you give me the trouble codes.

The service engine soon light indicates you have a problem with the engine management system.The only way to get it to stay off is to lacate and repair whatever is not working correctly. Requires very specialized equipment. Take it to your mechanic.