I have a persistent p0466 on a 2003 Silverado. I have changed gas cap, purge sensor, evap sensor, and charcoal canister , but it keeps coming back. Any ideas.

 

No but you have replaced all the things a code P0466 would call for. I am stumped as you are.

 

Have you checked the hose that goes between the charcoal canister and the purge valve for cracks? What about corrosion around the top of the gasoline filler neck?

 

the pcm is monitoring the fuel tank pressure sensor to determine pass fail...you should monitor it to.
with the fuel cap off, the pressure should read near 0"h20
when the system is purging the pressure should drop; if you see no change in the reading either the purge flow is blocked..ie clogged line or the ftp sensor is bad.

 

I must apologize for I misread the OBDII code you provided. I was thinking it was a vacuum leak code. A big thank you to tech2 for waking me up and causing me to look at the initial thread more carefully.

About 3 years ago my 99 Silverado threw the P0466 code, and it turned out to be the fuel tank pressure sensor. When I investigated replacing the fuel tank pressure sensor (which on my Silverado is located on the fuel pump assembly), everything I read mentioned having to drop the fuel tank in order to replace the sensor.

Well, I discovered that after I placed the truck on jackstands, I was able to get one of my arms to go up and over the frame railing and I was able to touch the electrical connectors that plug into the fuel pump assembly. Using an inspection camera, I was able to figure out that after disconnecting the electrical connector to the fuel tank pressure sensor, I could stick a small to medium sized flat bladed screwdriver under the fuel tank pressure sensor and pry it out. It worked! I put in a new fuel tank pressure sensor, connected it and I have not been visited again by the P0466 code. I was sore for a couple of days, but it sure beat having to drop a full fuel tank!!!

Good luck!