PulpFriction

Today I connect the scanner and see the alcohol content is now calculated to be 11%, which is great, because I had checked a couple times since my last post on this thread and it was still at 0%. I have no idea why it took so long to make up it’s mind.

The long term fuel trim was 5-10% or less, which seems OK. It’s running great.

The reason I scanned is because the CEL came on for my wife. It’s a P0442 (small evap leak.) Hopefully unrelated. Cleaned the filler cap seal, cleared the code. Will lecture wifey on making sure the cap is tight and hope it doesn’t come back.

donbrew

Most codes, like P0442 clear themselves once the condition is remedied. Not wise to knee jerk clear codes.

PulpFriction

Yeah, but I didn’t know how long that would take and I wanted that CEL off so she wouldn’t be anxious. Also reminded her to turn the engine off before refueling. So far, so good.

PulpFriction

Not so good.

P0442 small evap leak kept coming back, all the way into December. When it was warm, living with remote start was no big deal, but…

So I took it to my most trusted shop and asked them to smoke test it, knowing that the procedure might be futile for a “small leak” and it was, so they just took a shot in the dark and put a new vent valve in. That was 3-1/2 weeks ago so I’m tentatively calling it fixed.

Oldblue

The EVAP vent valve under the rear axle or the purge vent valve under the hood, just to clarify.

PulpFriction

Now been going on 6 weeks, so calling the evap valve the fix for my P0442 evap slow leak.

No more problems with P0172 after over a year and a new cold weather onset, so calling resetting the obviously erroneous ethanol % the fix for that (after fixing the common fuel line leak that everyone gets.)

RJ_RS_SS_350

Awesome! Thanks for the update.

Oldblue

Would you please verify which valve fixed the problem.
I scrolled back several pages, and saw you took your car to a dealership for the ECM reflash and they reset the alcohol content.
This isn’t something so simple to do then , someone mentioned a dongle and a free app.
Sorry, I’m at the hospital right now with Sweetie starting her 3rd round of chemotherapy, could you, post the procedure in a how to, or post it here and I’ll move it later. Thanks

PulpFriction

Sorry, the vent valve as previously mentioned. The one in the back. But talking about the P0442 here was a bit off topic, had nothing to do with the P0172 as far as I can tell. I shouldn’t have mentioned it here.

Just to recap so this might make sense to someone later -

My P0172, and cturboaddict’s, and one other I know of, were caused by a high stored ethanol %, even the though the tank contained regular.

As I mentioned in the other more recent P0172 thread, just checking the stored ethanol % is pretty easy.

Sampling and testing the actual content of the tank is a little more work but not that bad, and should be done if the stored value is a surprise, just to prove it’s wrong. Resetting is a PITA unless you have access to a high-end scan tool with that capability.

An additional though is that resetting (to zero) makes sense if the tank contains regular, i.e. 0-10% ethanol, but the stored value is high. This was true in the aforementioned cases. I don’t know what to do if the stored value is otherwise out of whack.

The comments by Donbrew and by cturboaddict (the OP) were most helpful as I stumbled my way through this.

Oldblue

Thanks, that’s going to help future readers.
interesting reading here in post #4 from ChevyMgr

https://www.chevyhhr.net/forums/gene...ex-fuel-18111/