I have a 2004 Yukon denali and while driving, I got check gas cap alarm. 2 miles later check engine light is on. Checked gas cap, cleaned gasket and tightened. Drove for 2 days. Reset fault and drove 160 miles. Then found monitor for evap. Didn't reset. Started in the morning and let it idle for 3 min. Then drove on thruway for 10 miles at 65 MPH. Stopped and idled for 3 min. Drove around city. Still didn't reset. Did the process again now over 300 miles. No check engine light or anything pending. Went to dealer and bought a new gas cap, drove around city again and still no check engine lights or faults? How do I get this monitor active for NYS inspection. John

You need to take it and have the codes scanned. Sounds like a misfire in the ignition system.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/justin_3ae27a9d61d6acd4

throttle position sensor is prob. bad. unfortunately this mean replacing the throttle body

Doesn't completely sound like a fuel pump problem...sounds like a vacuum line problem .... check your pcv ...and vacuum lines and when was your fuel filter last changed and how many miles are on the car...your fuel pressure regulator solenoid needs to be dry on the vacuum side too...diaphram could be leaking but if you can't find an obvious problem I would definiately find a qualified mechanic to dive into it...do you have access to a scan tool to read the trouble codes?

It may be a loose fuel cap or it is worn out already. Check also the hoses leading to and from the fuel tank for loose or bad ones that need replacing.

Go to an Advance or Auto Zone and ask them to read your fault codes. This is a service they will do for free in hopes of selling you a replacement part. You likely have a faulty sensor that is causing the light to come on. Good Luck! I hope this is very helpful!

Hello tdamm...No...the service engine soon (SES) light on your yukon is not telling you to change the oil.
This is a warning light that is illuminated when there is a problem affecting the Emission system and the engines computer management (ECM) has detected it from a fault. It could be something as simple as a loose or defective gas cap. If the SES light is blinking, it's more serious....
The yukon needs to be connected to diagnostic equipment (scanner) for fault diagnosis.
You can go to autozone they will hook up an OBD II scanner to your vehicle and explain the codes to you.
Good luck...i hope this helps and will fixya up.

dear sir the flashing check engine light means the truck was misfiring at the time of the incident .If the light is still on you can go to auto zone they will pull the codes for you and reset the light if you like.but if running good now then probably nothing to worry about .

The gasket or large o-ring on the under side of the cap might be warn not keeping a tight seal. replace gasket or o-ring, or get a new cap, and see if that cures it.

FROM: LustyKid

Denalis are famous for clogged fuel filters. Change the fuel filter first and see what happens, Get the code for the check engine light. It could be you have a clogged EGR ports. Remove EGR valve and clean out the ports, replace with new gasket and see what happens. Advise of results.

Did u put in fuel shortly before the light came on? I own 2 service centers & the most common situation with "Check Engine" lights are because the fuel cap wasn't re-installed or not tightened. When you refuel make sure it "clicks" when putting back on. We don't charge for a "Code Reading" but a dealer will, don't go there. Go, like the others suggested. If it is the fuel cap & you re-install it correctly, the light will go off after a short drive. Good Luck. PS-Don't panic when the "Check Engine" light comes on unless it blinks, if that happens don't drive. PSS-RE: Murray's, Auto-Zone.......If it's a "Code" (the reader will give a #) the code book will tell you the problem. PSSS-Some1 please have Troy W's Mommy & Daddy take away his keyboard. Just because you can put together a "Lego" car doesn't make you a master mechanic. You only repeated what we said except you have a "Napoleon" complex against any1 plugging something in to a vehicle. It's the same as plugging in a light @ home. In conjunction with "kinder" nine out of ten time in my experience it usually is the oxygen sensor(s) which would be about right with the year model