I am continually getting P0452 after starting my '98. I have cleared it with scan tool, but scan tool won't clear the pending code. I have been told and seen several threads that it is commonly the gas cap. If P0452 is too much pressure (low voltage) and P0453 is too much vacuum (high voltage) in the gas tank, it doesn't seem that a leaky gas cap could cause either of these. In fact I would think that it would make it impossilbe to cause this code by itself.
I had a buddy drive his Blazer around with no gas cap and he only got code P0440. No P0452. I have tried a new cap, but after researching more I would be curious if a faulty gas cap has EVER caused this code??? And if so, based on my above ASSumption, why?

After I check the low sensor voltage at the ECU side, I am going to have fun dropping the tank to check the sensor / connection / wiring. Anyone know of a common failure point besides the gas cap??

 

P0442 can be caused by a faulty gas cap. I would strongly doubt that the gas cap would cause a P0452.

Have you stepped down through the diagnostic sheet:
P0452 - Evaporative Emission Control System Pressure Sensor Low Input

 

Thanks for the diag sheet! This looks very promising and much more methodical than trial and error replace. I'll report how far I have to go on it. and how painful.