Friend's Esky throws EVAP related codes.

[Pandabird]

Just an acquaintance from whom I've bought some kickass second hand parts having a bit of trouble with his Escalade.
Says he's trying to figure out an EVAP problem. Has apparently swapped topcover gaskets, gas cap and one evap hose.
Says the computer asks him to "tighten his gas cap" followed by codes p0454 or p0455
Problem is a once in a while thing, can run for weeks without.

If it sounds all too familiar remember it's all new to me. Same year as mine.

 

[Fless]

EVAP test is done only on a cold start, with many other conditions being met: fuel tank 1/8 to 7/8 full, ambient temp within around 11° of ECT, etc. So not on every start, which means it can take a few days between attempts.

Failure can be caused by canister vent valve or purge valve malfunction, canister soaked with gas (caused by over-filling the tank), a defective fuel tank pressure sensor, along with others.

SOLVED - P0449 still persists after changing out charcoal canister and both valves?

2018 Escalade ESV with 131,000 miles I got P0449 a week ago and finally got all of the parts together to change out the related components. I used all ACDelco components to change out the charcoal vapor canister (84106549), vent valve at the back (84148820) and purge valve on the engine...

www.tahoeyukonforum.com

Mike shows the purge and seal test along with some good information: