Codes 34 & 41
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 432
Likes: 0
From: Germantown, MD
Codes 34 & 41
I pulled KOER codes today on my '86 F150, 108,000 miles, 302 EFI. I got a code 34 - PFE or EVP circuit above the closed limit of 0.67 volts; and a code 41 - No HEGO switching detected always lean (right side). I cleared the codes and ran it again and they came right back.
Last week I fixed the pipe that feeds the EGR unit (it had rusted out). But, I still have the EGR code..
Seems like maybe my EGR is feeding the engine too much air causing the lean condition hence the lean code and the EGR code. How should I approach this?
Last week I fixed the pipe that feeds the EGR unit (it had rusted out). But, I still have the EGR code..
Seems like maybe my EGR is feeding the engine too much air causing the lean condition hence the lean code and the EGR code. How should I approach this?
Moderator
Joined: Jan 2001
Posts: 56,846
Likes: 2,681
From: Virginia
Move the egr by hand to make sure it's not stuck. I think you are correct, it's not closing all the way, and the computer sees this as the voltage reading from the feedback sensor is too high. You may also take it apart and see if there is a piece of carbon hanging it up and not letting it close.
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 432
Likes: 0
From: Germantown, MD
Ah ha! I was under the hood looking around before I began removing the EGR for cleaning and inspection when I noticed a small vacuum leak. The leak was under the hood near the battery on a manifold of vacuum lines. I believe the leak was preventing the EGR from receiving the ported vacuum signal it requires as well. The truck runs much, much better.
It still has a very slight miss under mid to heavy load at low RPMs (same conditions). The problem is 90% better, but about 10% of it still remains. I am going to clear the codes, drive it for a while, and see if they come back.
I am also going to upgrade to a 3 wire heated oxygen sensor to get the system online faster.
It still has a very slight miss under mid to heavy load at low RPMs (same conditions). The problem is 90% better, but about 10% of it still remains. I am going to clear the codes, drive it for a while, and see if they come back.
I am also going to upgrade to a 3 wire heated oxygen sensor to get the system online faster.
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 432
Likes: 0
From: Germantown, MD
The EGR code did not return. But, the code 41 remains, which is no O2 switching sensed. I ran the test with the truck warmed up, but I have LT headers and the O2 sensor was moved downstream at the collector. Is it possible that it is just not getting hot enough to produce a voltage signal?
If it's not the O2, then it must be running lean. Now, I do have some HVAC issues I have been looking into. It is possible there is a vacuum leak under the dash in the HVAC stuff, but I don't think that would be enough to cause no O2 switching..
If it's not the O2, then it must be running lean. Now, I do have some HVAC issues I have been looking into. It is possible there is a vacuum leak under the dash in the HVAC stuff, but I don't think that would be enough to cause no O2 switching..