Can't get the oil fill cap off of my 03 dodge ram truck

What color is the exhaust? Check your water level and oil.

You have excessive blow by most likely sue to worn pistion ringssw

check the cat. and the sensor/s on the exhaust pipe. change air filter and plugs clean out the intake. and check the EGR valve. there the main problems with an emissions fail. failing that check oil and water look for water in the oil (filler cap has white film on the inside). water look for a shiny oil mark. in still water. if any of them or both then that could be you problem head gasket has failed.

Check out the related help links,with solutions to troubleshoot the problem:-----Click the link below:-----------Common Causes of Car Oil Leaks? http://schematicsdiagram.blogspot.com/2011/12/common-causes-of-car-oil-leaks.html
--------- Troubleshoot Car Oil leak? http://schematicsdiagram.blogspot.com/2011/12/troubleshoot-car-oil-leak.html
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2000 Dodge Ram 3500 Cummins Diesel: Oil Leak issues? http://schematicsdiagram.blogspot.in/2012/06/2000-dodge-ram-3500-cummins-diesel-oil.html
-----------How to Check Differential Oil Leaks and Replace Oil
http://schematicsdiagram.blogspot.com/2011/07/how-to-check-differential-oil-leaks-and.html

HOW TO PERFORM A BASIC ENGINE TUNE UP-OIL CHANGE
http://schematicsdiagram.blogspot.com/2011/08/how-to-perform-basic-engine-tune-up-oil.html
-----------High Oil Level on Dipstick http://whatisbyme.blogspot.in/2012/06/high-oil-level-on-dipstick.html
---------------- Oil light came on and the car died? http://schematicsdiagram.blogspot.in/2012/03/oil-light-came-on-and-car-died.html
-------------- How to replace Oil filler cap or breather cap? http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-oil-filler-cap-or.html
---------------- Oil pouring out from left front of engine? http://schematicsdiagram.blogspot.com/2012/01/oil-pouring-out-from-left-front-of.html
--------
These details will help.
Thanks.

For your help, there are few Car Engine oil related solved problem listed below. You can go through it.
High Oil Level on Dipstick http://whatisbyme.blogspot.in/2012/06/high-oil-level-on-dipstick.html Oil light came on and the car died? http://schematicsdiagram.blogspot.in/2012/03/oil-light-came-on-and-car-died.html How to replace Oil filler cap or breather cap? http://repairhelpcenter.blogspot.in/2012/02/how-to-replace-oil-filler-cap-or.html Oil pouring out from left front of engine? http://schematicsdiagram.blogspot.com/2012/01/oil-pouring-out-from-left-front-of.html Common Causes of Car Oil Leaks? http://schematicsdiagram.blogspot.com/2011/12/common-causes-of-car-oil-leaks.html Troubleshoot Car Oil leak? http://schematicsdiagram.blogspot.com/2011/12/troubleshoot-car-oil-leak.html 2004 Dodge Stratus: Windage Tray Problem http://howtobyme.blogspot.in/2012/07/2004-dodge-stratus-windage-tray-problem.html Toyota Highlander Sport Oil change details? http://repairhelpcenter.blogspot.com/2012/01/toyota-highlander-sport-oil-change.html Low oil pressure light on Dodge Magnum?
http://howtobyme.blogspot.com/2011/11/low-oil-pressure-light-on-dodge-magnum.html

Kia Sportage leaking oil from oil pan?
http://howtobyme.blogspot.com/2011/11/kia-sportage-leaking-oil-from-oil-pan.html
Car Turns OFF due to low oil pressure warning light?

http://schematicsdiagram.blogspot.com/2011/12/car-turns-off-due-to-low-oil-pressure.html
Toyota Corolla leaking oil from timing cover? http://technoanswers.blogspot.in/2012/02/toyota-corolla-leaking-oil-from-timing.html

Overfilling oil in engine?

http://whatisbyme.blogspot.in/2012/06/overfilling-oil-in-engine.html
2000 Dodge Ram 3500 Cummins Diesel: Oil Leak issues? http://schematicsdiagram.blogspot.in/2012/06/2000-dodge-ram-3500-cummins-diesel-oil.html-----------
These will help.Thanks.

I had the same problem with this truck as well. If the gas cap is loose it can cause the check engine light to turn on. Try tightening the cap well each time you fill up. If this does not help you may want to try replacing the gas cap. Hope this was helpful.

You will need, 6 qts, of 5w-30 oil, hope this was very helpful.

on top of the motor in front

p0440 - Evap. system performance (this could be something as simple as not turning the gas cap several times after you fill up.

p0456 - Evap leak monitor Small leak detected. - Could be related to the previous code.

p2106 - Throttle Actuator Control System - Forced limited power : This one you might have noticed the vehicle running rough, overdrive not working properly and cruise control will not set.

p2175 - Throttle Actuator Control System - Low airflow detected.

What you might want to try first is have the codes cleared which most auto parts stores offer this for nothing (unless you have a programmer then you can do it yourself). Pour in some fuel injector cleaner into your gas, put a new air filter on. And when you fill up your gas tank, crank the cap several times when you put it back on.
See if the codes come back on after that.

Look all around the housing for a fill plug about mid-way up from the bottom.
Unscrew the plug (ususally with a 3/8" ratchet extenesion) and pump in the correct gear oil until it just begins to drip out the fill hole. Replace the plug snugly.