Hey everyone, just thought I'd post this in case it helps someone. For a couple months now I've been trying to clear all the codes off my truck ('98 Tahoe 2 Door) for the local emissions testing (they wont even test you if the SES light is on). I've read through numerous different forums and couldn't find a solution to fix my problem for the pesky P0452 code. I blew the Evap canister out with compressed air and cleaned the foam filter and Vent Control module to clear the P0446 codes (also hooked the module to power to verify it was opening and closing smoothly). However no matter what I tried I couldn't clear the P0452 trouble code. I checked power to the pressure switch and had a constant 4-5 volts (normal) and it is venting properly because there is no pressure releasing when I remove the gas cap (low voltage = high pressure). So it came down to replacing the pressure switch, but it is attached to the fuel pump on these vehicles and you have to buy a whole new pump assembly and drop the tank. I was able to pull the pressure sensor off an old fuel pump I had, cleaned it up, and installed it in the top of my existing fuel pump without dropping the tank (just pulls straight out and seals with the rubber grommet). Cleared the codes and drove it for a few days to make sure it didn't come back, tested it today and passed with no pending codes in sight! So the short and skinny of it, if you have a vehicle with the attached pressure sensor that isn't sold separately, go to the wrecking yard and pay $20 for an old fuel pump and simply swap out sensors, rather than $250-$350 for an all new fuel pump. Sorry for the long winded post, but if I would have found this months ago it would have saved some time and the need to drive with expired tabs.

 

Welcome good information hope it helps many in the future