Hi everyone, I am getting these 3 codes. P0101, P0140, and P0161. I know I have an exhaust man. leak on the pass side but would that cause this? Could it be an intake gasket? Any info would be helpful. It is a 2003. 6.0L engine. Thank you.

 

PIP4925B

 

Manifold leak? All consistent with plugged cats.
H2 are notorious for plugged cats throwing a bunch of codes at once. The back pressure could also be causing the manifold leak.

Easy to check. Throw a pressure gauge into the o2 sensor holes that are before and after each cat, and you have your answer.

I dropped $3K on OEM replacement on ours for that exact reason. O2 sensors will need replacing as they will break trying to free them, and the manifold are all one piece with 2 cats attached. Nuts!

 

I removed the O2 sensors on my 2003 no problem or breaking. I did spray them with some Kroil while they were warm about 30 minutes before I removed them though. Plugged cats will generally make it run very poor in addition to throwing codes. If they are plugged and it runs terrible another check is to just remove the upstream sensors. It is suddenly starts running much better (will still have check engine codes) then yeah, cats are clogged and the open sensor hole is giving the exhaust somewhere to get out.

Intake gasket can cause issues as well and the original gaskets are known to harden and leak. While care must be taken you can spray around the intake with carb cleaner while it is idling to try and check for leaks. If the idle suddenly changes at any point there is a leak and it sucked some in....