P0401

I been getting this code on and off since I got the truck 3 years ago but it wasn't until recently that we started hauling a boat and I've noticed the code goes away whenever the O/D Off light is on.

Tried everything and even replaced the EGR valve and did a whole bunch of troubleshooting. Could there be a connection between high rpms and the P0401?

 

So I had a P0402 code recently, which is the opposite of an P0401, but I think they have similar origins. Mine turned out to be clogged vacuum ports in the throttle body.

High rpms is a low vacuum situation if i remember right, so if something is clogged that could cause an issue.

I ended up trying to blow through all the different tubes connected to the throttle body and found a couple that were nearly impossible. A quick pressurization from the air compressor took care of that.

Also, what condition are your vacuum lines in? A leak could be a problem too.


Lastly - have you tested the EGR temperature sensor? If its not working right you can get codes from it (in fact its a pretty common cause)

 

I checked all the vacuum lines and even replaced a few that looked old.

I'm starting to wonder about the temp sensor.
I'm going to check.

What's interesting is that if I haul my boat for about 45 mins the light CEL stays off for a while, I drive this truck almost everyday with the exception of weekends and it does stay clear but after a few days, sometimes weeks, the CEL comes back.

Thanks for your input.

 

Did you ever find a fix for this?

 

I had the p0401 forever and it keeps coming back. Whats happening on my truck is the maf and egr temp sensor get dirty. Clean both and it goes away. Also new air filter helps.