2000 Sonoma- P0452

Hi guys, you've helped in the past, so here gose:
2000 GMC Sonoma 4.3L, 4x4, A/T,160,000 mi.
It has ap0452 emissions sensor circut, but it only sets a code when the A/C is run, not def., . HELP!!!!!!:confused:

Google the code plenty of info, or do a site search also plenty of info.

P0452 is the code for Fuel Tank Pressure Sensor Circuit Low Voltage. The only possible causes of this code are a faulty FTP Sensor, faulty ECM, or a wiring problem between the FTP Sensor and the ECM. Here is a link to the GM service manual for that code. Hope it helps!

http://gsi.xw.gm.com/si/showDoc.do?docSyskey=556479&cellId=28351&pubObjSyskey=556479&from=sm&pubCellSyskey=28351&deliveryEffectiveDate=Jun+1%2C+2010

I have alldataonline, I've done the pin pont test, every step passes.
Also I forgot to say that the A/C has an exsseive amount of condensasion.

The A/C shouldnt have anything to do with it. Did you check the harness at the fuel tank pressure sensor and do a drag test on it?

Sounds to me like you have a problem with your ECM because the circuits that control the fuel tank pressure sensor do not interfere with the circuits that control the A/C. The only place they meet is in the ECM so I'm gonna say you have a bad ECM.