Just looked, I haven't posted in 10 years, time flies. I have a 2004 pace arrow with 8.1 Chevy, I am getting engine code P0131, which puts the engine into a fail safe mode, thus losing power. My question is pretty simple, just can't find anyone that thinks I am on the right track.It started in the Fall on a trip after I got gas, and then it went away after I got gas again, then came back after I got gas again..........sounds simple, maybe a gas cap.So I buy a new gas cap, worked great for another 1200 miles of towing, then it happens again under load. I mess with gas cap, it goes away for 150 miles and then on a long climb it comes back.The code says it is a lean condition on the left side o2 sensor, I replaced that as well.So my question, am I on the right track with the gas cap? If it isn't sealing correctly, it can't create a vacuum, thus the computer will throw an engine code?? Can't find anything on the internet to confirm this theory.This has only happened under heavy towing on a hill as well. Clear code and it goes away, until the next climb.Any ideas appreciated,.

There are numerous possibilities. If you know of a good mechanic with a top notch scan tool they can look at fuel trims and other data to narrow the actual issue down. Common causes for the P0131 code can be from the 02 sensor which you already replaced to fauty sensor wire harness, a clogged fuel filter, fuel pump going bad, leaking exhaust at the donut, Intake air leaks, faulty injector, etc....

Do you have a exhaust manifold leaking on that side? Have fuel trims checked.

Two different replies here said cleaning or replacing the MAF sensor cured their issue. For what it’s worth I just replaced the one on my 2005 8.1l. I was getting p0101 when pulling grades after a gas stop It turns out the MAF test only runs when near WOT and it takes 2 consecutive failed tests after restarts. That’s why mine also seemed to track with gas stops followed by grades.It has under 40k miles but obviously they age out. I tried cleaning first then replaced it and the MAP sensor. No more codes. Just over $100 for both if I remember correctly. Granted, mine may have been the MAP sensor but I wanted the issue gone and "testing" was only during infrequent trips.

I have never seen a o2 sensor put a gm in fail safe mode I have seen a throttle body that's drive by wire do that

I am using the moho again this weekend not towing and no hills, short trip to the beach. I have cleared the codes and bought another gas cap. Let's see what happens.........

Chevy Workhorse 8.1 going into limp mode | Good Sam Community

wrgrs50s
Explorer
Feb 21, 2018
There are numerous possibilities. If you know of a good mechanic with a top notch scan tool they can look at fuel trims and other data to narrow the actual issue down.

Common causes for the P0131 code can be from the 02 sensor which you already replaced to fauty sensor wire harness, a clogged fuel filter, fuel pump going bad, leaking exhaust at the donut, Intake air leaks, faulty injector, etc....
rwynkoop
Explorer
Feb 21, 2018
Do you have a exhaust manifold leaking on that side? Have fuel trims checked.
wnjj
Explorer II
Feb 21, 2018
Two different replies here said cleaning or replacing the MAF sensor cured their issue. For what it’s worth I just replaced the one on my 2005 8.1l. I was getting p0101 when pulling grades after a gas stop It turns out the MAF test only runs when near WOT and it takes 2 consecutive failed tests after restarts. That’s why mine also seemed to track with gas stops followed by grades.

It has under 40k miles but obviously they age out. I tried cleaning first then replaced it and the MAP sensor. No more codes. Just over $100 for both if I remember correctly. Granted, mine may have been the MAP sensor but I wanted the issue gone and "testing" was only during infrequent trips.
allbrandauto
Explorer
Feb 21, 2018
I have never seen a o2 sensor put a gm in fail safe mode I have seen a throttle body that's drive by wire do that
Alxcook
Explorer
Feb 21, 2018
I am using the moho again this weekend not towing and no hills, short trip to the beach. I have cleared the codes and bought another gas cap. Let's see what happens.........
Ron3rd
Explorer III
Feb 21, 2018
allbrandauto wrote:
I have never seen a o2 sensor put a gm in fail safe mode I have seen a throttle body that's drive by wire do that

X2, and I was not aware the leaking gas cap could put you in limp mode, though it will throw a code.
wnjj
Explorer II
Feb 21, 2018
Alxcook wrote:
I am using the moho again this weekend not towing and no hills, short trip to the beach. I have cleared the codes and bought another gas cap. Let's see what happens.........

Again, please consider the MAF if you still are having issues. In addition to the 2 replies in the thread in my other post, there's one in here too:

http://www.rvforum.net/SMF_forum/index.php?topic=87335.0
bucky
Explorer II
Feb 22, 2018
allbrandauto wrote:
I have never seen a o2 sensor put a gm in fail safe mode I have seen a throttle body that's drive by wire do that

x2. Sold hundreds of TBs on that gen of GMs. Pull over and 10 minutes later it can be fine for 6 months or an hour.
BurbMan
Explorer II
Feb 22, 2018
allbrandauto wrote:
I have never seen a o2 sensor put a gm in fail safe mode I have seen a throttle body that's drive by wire do that

^^^ This^^^

There is no vacuum in the fuel tank. The fuel is pumped by the in-tank pump and unused fuel returns to the tank via the return line. There is a vapor line that runs vapors through the charcoal cannister, and periodically the PCM will command the fuel tank to be pressurized slightly to check for air leaks. If the gas cap is loose/faulty it will usually throw code P0440 and light the CEL.

I think the gas cap is just coincidental to whatever the real problem is.
Alxcook
Explorer
Feb 22, 2018
Thanks guys, certainly sounds like a MAF.

We all know how these motorhomes are create (virtually one of a kind), I am assuming the MAF is right after the air cleaner?

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