How to reset Service Engine Soon light after replacing gas cap? Took to AutoZone when the Service Engine Soon light came on Error code P0440.

http://www.obd-codes.com/p0442
P0440 indicates the failure of the EVAP system to develop proper vacuum. If you got
and replaced a proper good quality gas cap, you have corrected the most common cause.
However, in fully searching the causes of this code (http://engine-codes.com/p0440_chevrolet.html ) (pardon the generic GM info, but will apply for you)-----you will find there are 5 other causes of the vacuum failure, which are independent of the gas cap. Your good local mechanic can sort those out; I would save your gas cap
receipt if you were advised to buy one not needed. As you probably know, your
State emission test facility checks your gas cap----so that is another way to find that specific portion of this answer,
(for their fee).
P0300 is a generic misfire code. For this, a specific Cadillac forum may be most
helpful = 2001 Deville intermittent service engine soon light code P0300
2001 Deville intermittent service engine soon light code... I recently bought this car from an owner who took decent care of it but a week after i bought it, the service engine light appeared. After a few View on www.cadillacforums... Preview by Yahoo You will see that this generic code is perhaps more serious, costly, and harder
to track down than the P0440. You will also discover that P0301 is cylinder 1 misfire, P0302 is cylinder 2, and etc, etc. If you get a good diagnostic, they will generally
be able to localize the problem fairly specifically---and get a more specific fix. The person who reported this code was unhappy because he was given several ($$) fixes,
before he got one that erased the code, and was a solution. (Be forewarned ----A generic misfire can have umpteen issues--or one! !; use your own local preferred method for solving this with a mechanic who gives you good service, and stands behind what they do.)
2001 Deville intermittent service engine soon light code P0300

P0440 EVAP mulfunction , EVAP valve or hoses leak

A code P0440 could mean one or more of the following has happened:

• The gas cap is not installed or working properly
• The purge solenoid has failed
• The canister is plugged and not working properly

With a P0440 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

• Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
• Inspect the EVAP system for cuts/holes in tubes/hoses
• Inspect for damaged or disconnected hoses around the Evap purge solenoid
• Check and/or replace the sensor
• Check and/or replace the purge valve
• Have a professional use a smoke machine to detect leaks

Get a new gas cap first to try.
thanks

Here are some possible causes and fixes http://www.obd-codes.com/p0440

code p 0440 refers to the EVAP system --purge valve malfunction
check wiring and replace the purge valve

Sometimes you have to wait a week for the light to go off, the computer has to go through several start/run/stop cycles.

If you have an Advance Auto Parts store where ever you are, they will read the code and tell you exactly what to code is and what it means. Any mechanic who "guesses" isn't a mechanic at all - he's a thief. Emissions leak can be any number of things, but not the gas cap!

You have to have one of the parts stores clear it. Did you check you gas cap. P0440 Is an emissions codes usually caused from a loose gas cap

P0440 is a EVAP leak detected, try changing the gas cap and reseting the ECM to clear the service engine light. If you can not clear the code it takes about three start up with out any issues to clear the code and after 100 start up's the codes will clear from the ECM's history. Note use the GM OEM gas cap for a replacement, anything else is just garbage and you'll be replacing it again with in 6 months. If it's not the gas cap, need to take it to a garage and have them do a smoke test to locate the leak in the system. Good luck and hope this helps, keep me posted. be glad to help

wow thermostat >>>> shucks i believe its evep emissions code like faulty gas cap ....you can reset any computer the chck eng light will come on in 50 to 100 miles if not fixed....