My niece's car (2015 Chevy Sonic 1.8) had a check engine light. Codes were P0131 02 Sensor Low and P0171. I replaced the $144 02 Sensor and light went away. I did notice a hissing sound from the valve cover but it was low. I thought it was odd, I then took the car out and it ran fine. I could feel a slight hesitation but still ran and didn't turn off like it was.

Today she calls back and said the car shut off again. Light was on and ran the diagnostic. Same two codes came back. Checked all the hoses the intake boot and all good. That hissing sound I heard yesterday was really noticeable today. Anyone had this issue. The air is coming from a port on top of the valve cover. Its gotta be a leak. Just wanna see what yall think. Its a 50 dollar fix. Kit comes with a new valve cover and pcv.

 

are you sure air is coming OUT of there, and not going in? If so then PCV is probably bad.

 

Hi Mr Joe, im back again...Feels like the air is coming out. I shoulda put a piece of paper to the area when I was there. But you're right it is the pcv valve. I just found a youtube video on what im dealing with. The new valve cover is on the way. I see the torque specs are 71 inch lbs, but can't figure out the sequence and I read some bolts need some thread sealer. Just looking through the webs for a diagram.

 

https://charm.li/Chevrolet/2013/Soni...0and%20Repair/

 

Got it Mr. Joe, gonna tackle this fix on Saturday. Waiting on a e torx socket set.

 

The sonic is fixed. Hissing sound gone with new valve cover and pcv. There was oil where the spark plugs go and we broke the coil pulling it out. So we replaced it and new plugs and she's running great

 

good work 👍
Thanks for reporting back.