When I bought my 2000, it did exactly the same thing.....pressure on the gas, nothing at idle, with accompanying chime tone and warning light. So I got a sender off of RockAuto, and my problem turned upside down, hahahah.
Now I have no pressure when I hit the gas, and great pressure at idle. I have a replacement sender to install.
I'll gladly report back with my pressure readings when I get a sender in it that works, LOL
2000 Grand Cherokee Limited 2wd, 4.7L V8 - It's blazing fast, blue, and the heap of Jeep.
2002 Dodge Ram Quad Cab 2wd, 4.7L V8 - Hailstoned, windshield cracked, storm chasin' truck. But dependable.