2001 Porsche 911 Check Engine Light when Fuel tank 3/4 full

hi ive seen this before you may need to just change the o2 sensor or you might try looking at the canister or {carbon canister} it collects fuel vapor theres a in line one way valve somtimes fuel make its way past it into the can ...unplug the hose to see if its wet or smelles srong of gas .....it a easy thing to check ...you can look this up at www.pelicanparts.com look at the onlin diagram you can put this number in the search box {99620122109} it will pull up a diagram of what to look for ok" but this is providing youve already changed the o2 sensor .

The odd thing is that the codes indicate that both O2 sensors are defective. I had replaced the carbon canister and filler cap as my mechanic said it might be vapor leak and the vapor pressure is checked when the gas tank is 3/4 full and then again when it is 1/4 full. The codes are indicated by Durametric. When the tank is full I can reset the Check Engine codes but the Check Engine light comes back when the tank is 3/4 full with the same codes.

often times the o2 sensors can blow out at the same time or one shortly after the other...like if sensor #1 {the one closest to the eng }goes first it offsets the air fuel mixture then sensor#2 the {one after the cat } over time gets clogged by the rich mixture or just works overtime ... holds on for awhile after that but eventually goes bad too" the control modual will make the necessary adjustments to keep it running somtimes running strong even with the bad sensors ... ive scaned alot of cars and if you erase the code only to have them re appeer' i would just change the sensors ... meanwhile i will be looking a bit closer at it to see what i might find ....good luck..... i hope this helped.