GM Vortec Swap: PO441 (Incorrect Purge Flow) Repair (1 Viewer)

[Taylorious]

So, your ECM seems to only have two things by which it can judge "Purge Flow". I assume it needs to see current flow in both of those solenoid valves shown in your photos. Do both valves have continuity?

Hey @spotcruiser, yea... it seems that both valves have continuity. Here's the values in Ω's:

AC Delco Purge Solenoid Valve / GM# 1997277 = 20.4Ω (both OLD and NEW)

AC Delco "Electrical Switches" / GM# 12556357 = 0.7Ω

AC Delco Purge Valve / GM# 1997201 = 28.4Ω (both OLD and NEW)

... but I'm into 3 new problems now.

#1) There's no way I can confirm successfully which canister vent valve the 1999 Tahoe uses.

Summit racing/Rockauto don't list anything but 1997277, and when I search "canister vent" or "purge switch" I get nothing.
Further, Part # 12556357's connector DOES NOT fit the harness connector. They're slightly different terminal Male/Females.

#2) I can't find a way to determine if GM# 1997201 is actually being used correctly in my application.

The parts fiches at any parts website list this part as NOT for a 1999 Tahoe 5.7L Engine. This is my main contender for the culprit, as it has comparatively high resistance to the 1996-97 GM#12556357 part and is being used in a way that is not it's original intended. Further, GM#1997201 it is not always "open" as GM#12556357 is, and requires some type of activation to open the internal blockage.
...so, from what I can tell, the 1996-96 diagram HAS a EVAP Purge Vacuum switch (see above images in post #19) and that my truck does NOT.

#3) The Bureau of Automotive Repair sticker on my door says "1996" for the model year of the engine swap, but the top of the intake manifold has "1999 Tahoe 5.7L" written on it.

This could be a potential issue as well.. since my harness was made presuming this was a 1999. That would explain how the connector doesn't match #12556357's port... but I dont want to just 'adapt' the part and connect them and see what happens... could be bad.


Current plan:

Replace GM#1997277 AND GM#1997201 in my truck with new parts, ensure the lines are not blocked, and see what comes of it.
Any other suggestions would be hugely appreciated... it's almost smog time.. and I need this code gone.

Are we having fun yet?
(GM#12556357 on LEFT and GM#1997201 on RIGHT)

 

[Taylorious]

Update:

Issue remains. P/O:441 triggered again this morning.

Unsure as to the cause at this point.

I think the next thing I'll try to do is find a 1996-1999 5.7L Vortec Tahoe and see if the owner/junkyard has a complete enough engine that I can take a look under the hood to see what similarities/differences exist in the EVAP System.

Beyond that, I'm stumped at this point.

 

[Taylorious]

Continued Update:

The new parts seem to have created a situation where the PO441 code is LESS likely, but still arrives.

If I baby it on acceleration and driving, it doesn't trigger as frequently (200+mi without a trigger has occurred)

The triggering happens at 1/2 tank or MORE full, and during hard acceleration for a freeway onramp.

Any thoughts?

 

[Taylorious]

THIS ISSUE IS CURED.

The problem?
The previous owner, or some errant mechanic, had wired this system completely wrong and put in non-appropriate OEM GM parts.
Specifically, GM# 1997201 was NOT for this vehicle, and didn't work with the system.

I had to go take a look at a junkyard GMT-400 Tahoe and see the engine EVAP diagram real-time.
As @spotcruiser showed me above, the electrical diagram showed 1/2 the issue, but I needed to see it real time since I didn't have the GM Catalyst/EVAP sticker under my hood to confirm.

Replaced with #12556357, re-plumbed the system from the solenoid to the canister, changed the electrical connectors to the correct connectors, and boom; Issue gone.

Thanks for the aide/interest, and hope this helps someone some day!

 

[spotcruiser]

Good going. Glad you finally found the issue.