Need help: P0171 and P0174 codes

[Colin]

Took Yukon (2010 XL 1500 w/5.3 liter engine) to shop to have rear main seal and pan gasket replaced. Got it back and it suddenly started throwing the 2 codes mentioned. They said they took apart my intake to do an oil pump pressure test.

So far, I've taken the intake off, cleaned it, cleaned the throttle body, replaced the MAF, and ran SeaFoam with premium fuel. I cannot audibly hear any vacuum leaks but I keep seeing the object circled and it looks like a hose should fit on it but there is no hose just laying around. It's sucking air in and when I put my finger over it, the engine RPMs drop.

Any idea what the circled item is and if it should have a hose on it? TYIA!

 

[Joseph Garcia]

YES, there is certainly something missing. I personally can't help you with that motor, but other GMT900 folks will chime in. @swathdiver @Charlie207 @SpareParts

 

[lspann3525]

that port should be capped off well at least on my 5.3 08 Z71 it is.

 

[lspann3525]

 

[LsHart]

Do u feel a vacuum on it? If not it's an option for a different engine.

 

[LsHart]

Took Yukon (2010 XL 1500 w/5.3 liter engine) to shop to have rear main seal and pan gasket replaced. Got it back and it suddenly started throwing the 2 codes mentioned. They said they took apart my intake to do an oil pump pressure test.

So far, I've taken the intake off, cleaned it, cleaned the throttle body, replaced the MAF, and ran SeaFoam with premium fuel. I cannot audibly hear any vacuum leaks but I keep seeing the object circled and it looks like a hose should fit on it but there is no hose just laying around. It's sucking air in and when I put my finger over it, the engine RPMs drop.

Any idea what the circled item is and if it should have a hose on it? TYIA!

That is a air leak after the mass air flow sensor. There for the codes u read. Cap it.

 

[Colin]

View attachment 476075

Thank you! Based on this picture, it almost looks like the cap was broken off from the neck-up on mine (which I think I've read that's happened to people before; I just didn't know what they were talking about). If anyone knows what that's called, I'd appreciate it. I don't want to just stuff a Qtip in it and hope for the best. I'd rather replace it w/an OEM part.

 

[strutaeng]

Take it back to the shop.

1. You've got a lean both bank codes, which is a classic intake manifold leaking unmetered air after the MAF.

2. You mentioned it feels (and sounds?) like a vacuum leak.

3. Those codes weren't there and you said they messed around with the intake.

4. You basically replaced the MAF for no reason, and with potentially aftermarket and failure-prone parts. Put the original back (cleaning it is a good idea) and leave the new MAF as a backup.

 

[Colin]

So, I wanted to post a preliminary update for anyone interested or having the same problem:

The port with the broken cap (mentioned above) seems to have been the culprit. I placed a piece of duct tape (don't judge) over the opening, cleared the code and have driven it 5-6 times various distances (up to 15 miles) and speeds (15-75 mph) since then and the code has yet to come back. Prior to the "fix", I would clear the code and it would come back almost instantly (at least within the first few minutes of the first or second drive). Bear in mind I did not notice any hesitation, rough idle, etc when the code was tripped so it was a somewhat elusive problem.

I will try to keep this thread updated just in case. Thanks for the help!