P0446

[goser]

Last week changed the fuel pump on 2001 Blazer, shortly thereafter I started getting P0446 codes. Anyone have any idea if there's something I might have done while replacing the pump to cause this?

[old_master]

P0446 is a malfunction in the EVAP vent circuit, (electrical). The vent solenoid is located on the frame crossmember just ahead of the fuel tank on your ZR2. It may have been bumped during the R&I of the tank, (the solenoid is pretty fragile). Another possibility is that the wire harness may have gotten pinched. Hope this helps.

[goser]

Thank you very much for the reply. I finally got a chance to get under there today, and the wiring looks okay... I certainly may have bumped the solenoid while I was wrestling with the tank under there. Is there a testing procedure for the vent solenoid? Thanks!

[old_master]

It's much easier if you remove the solenoid when testing it. The vent solenoid has one electrical connector with 2 terminals. The large fitting for the vapor line should have very little restriction if you blow into it. Apply battery voltage to one terminal and battery negative to the other. You should hear/feel the solenoid operate and you should not be able to blow into it.

[goser]

Thanks oldmaster. I removed the module and tested it with battery voltage. There was a very faint click of the solenoid activating... more distinguishable however was that the solenoid would rattle when de-energized but not when energized. However, I could not blow through the hose fitting in either state. It would appear the solenoid valve has seized. I recall reading that PO446 is only set when the fuel level is above 12.5%, and since the sending unit on my old fuel pump always read empty, it has probably been this way for a while and only threw the code once the new fuel pump was in and reading the correct tank level.

[old_master]

You're right, the solenoid is siezed in the closed position which will absolutely set a P0446.

As for setting the DTC: The EVAP monitor will only run its test if fuel level is between 15% and 85%. So, again you're right, the old level sender probably prevented the monitor from running, and now that it's reading correctly, the monitor ran its test, the system failed and set the P0446 in memory. Glad you got her fixed, and thanks for posting back.