I have never been under the hood of these newer Blazers yet so I can't speak from direct experience, but I would look at the recess to see if there is a fastener in there. If there is, remove the fastener and see how the cover moves. If there isn't a removable fastener there, you might just have to give it a tug to free the push in style rubber retainers that are typical on many engine covers. Before tugging though, give it a thorough inspection to see where it might be attached so you have an idea of where to apply force.

*Edit* - Well, I went looking to see if I could find some other pictures of the engine cover and it would appear as though the engine cover is more than it seems... It is also the air cleaner outlet resonator so it is coupled into the air intake system as well. That hose clamp onto the air intake pipe would need to be loosened and disconnected from the main air intake pipe to remove the cover. Just be careful not to drop anything into the open hole in the air intake pipe when the cover is off.

*Edit 2* - The video link below shows this cover, but doesn't go into specifics of how to remove it. I'll take some screenshots from the video to identify the fastener locations.



Red circles are the three mount points that will have a nut you will need to remove. 2nd picture shows the location of the studs on the top of the motor that the nuts will thread onto. Green outline shows the tube/sensor we are looking for.

 

Wow, I saw the thumbnail of this video on YouTube earlier but didn’t click on it because I assumed it would just be an overview without much detail. Swartlkk, thank you for finding the video and sharing such detailed information—it’s been a huge help! Now the fix seems much clearer and easier to handle.

Quick update (still ongoing, but I’ll report back tomorrow): I called the GM warranty line after my previous posting, and they confirmed that this issue should be covered under the powertrain warranty (my bumper-to-bumper warranty expired less than two weeks ago). I took the Blazer to the nearest dealership. At first, they said it wasn’t a powertrain issue, but later they mentioned they would "work with GM" to have the cost covered. While it’s there, I asked them to perform an oil change and tire rotation. They said it would take up to three hours in total, though I’m skeptical about that after seeing the detailed information Swartlkk shared.My Blazer is now staying overnight at the dealership.

With below-zero (Fahrenheit) temperatures expected in the coming days, I’d prefer to have the dealer address the issue under warranty. That said, thanks to Swartlkk’s insights, I feel much more confident about fixing it myself if the problem happens again in the future. Big kudos to Swartlkk!

 

Similar problem here but not covered under warranty on Gf's 2020 LT. Problem is that it's on nationwide backorder so I can't do anything abt it rn.

I've searched the web for replacement parts and it appears that it should be p/n 12718935. Ordered one online from a dealer that showed it to be in stock but they canceled the order and told us that it was backordered. Some sites show that it's actually been discontinued, while others just show out of stock. Anyone know if this is still the p/n? Anyone got a line on an available unit?

 

Thanks swartlkk for the Pics and pointing out how to remove the cover!, really was a great help.

I bought the sensor and replaced it, cleaned out the hose assembly (didn't seem to be any moisture at all), but so far hasn't helped with the code. I cleared it with a scan tool, but shows back up immediately upon starting the car. If doesn't clear after a couple days, may try disconnecting the battery for 15 minutes. Worth a shot. Really stinks that this code kills the remote start.

Edit: I ordered this part number: 12718935 they sent this part number: 12740187 Seems identical. website: www.gmpartswarehouse.com

 

Edit: Light went off after a couple of days after I changed this part and cleaned hose. Hopefully stays off. Remote start works again.