P0401 code, need help with EGR system (1 Viewer)

[Gunrunner235]

So been working on my LC and I keep getting P0401, I was getting P0171, but was able to clear it due to a vacuum leak. The 401 I keep getting, when I clear it it usually takes 50 miles for the CEL to pop back on. Here is what I have done, replaced both o2 sensors had to use the spacer for the rear bc the CAT was removed by PO. So is my LC always gonna throw this code bc CAT is gone? I tried the loop hoses trick on the erg right now, so far no CEL but I only drove like 10 miles today. Do I just need to do the resistor trick? Or just remove it? Bc I don’t think my ERG is even working, bc it doesn’t get hot at all. Any advice would be great. Just trying to clear the CEL and find out if I’m getting this code bc the cat has been removed and I’m just chasing my tail. Also did some SEAFOAM today to clean the intake and noticed I have a small exhaust leak at the manifold, I replaced the gaskets a few months back with OEM so I might need to tighten them down to spec. Anyways I haven’t noticed any real change in the way it runs, checked all hoses, seem good, maybe someone with the same issue has insight that can help me clear this code for good! Thanks in advance!

 

[aclos3]

Mine was solved by taking the throttle body off and cleaning the roughly pinky-finger sized port on the throttle body that mates up to upper intake manifold. These ports are well known to get fouled with carbon build up over the years. You should probably also replace the gasket that sits between the throttle body and the upper intake manifold when you do this job. The gasket is only a few dollars.

As for your exhaust leak, this could throw a code, but it would probably be something other than P0401 -- something related to O2 sensors or fuel mixture. The rear O2 sensor is there more as a confirmation for what the front is seeing, so I don't think this would cause a code, but I am not 100% sure on this.

 

[Bigjayva]

So been working on my LC and I keep getting P0401, I was getting P0171, but was able to clear it due to a vacuum leak. The 401 I keep getting, when I clear it it usually takes 50 miles for the CEL to pop back on. Here is what I have done, replaced both o2 sensors had to use the spacer for the rear bc the CAT was removed by PO. So is my LC always gonna throw this code bc CAT is gone? I tried the loop hoses trick on the erg right now, so far no CEL but I only drove like 10 miles today. Do I just need to do the resistor trick? Or just remove it? Bc I don’t think my ERG is even working, bc it doesn’t get hot at all. Any advice would be great. Just trying to clear the CEL and find out if I’m getting this code bc the cat has been removed and I’m just chasing my tail. Also did some SEAFOAM today to clean the intake and noticed I have a small exhaust leak at the manifold, I replaced the gaskets a few months back with OEM so I might need to tighten them down to spec. Anyways I haven’t noticed any real change in the way it runs, checked all hoses, seem good, maybe someone with the same issue has insight that can help me clear this code for good! Thanks in advance!

Im having the same problem with my 80. Any update on yours?

 

[Jeeper]

-Start engine.
-Pull vacuum hose between EGR modulator and the EGR valve with one end of hose still connected to the EGR valve.
-Prepare yourself and then suck on the hose to open the EGR valve
- if you cough and the engine sputters, the EGR valve is working
- consider replacing the EGR modulator

 

[subzali]

Do the FSM tests to see what is not working. It could be the VSV, modulator, etc.

There are some good threads on this site about troubleshooting it as well