Massey 4608 Limp Mode

I have a Massey 4608 that threw a 52020831 code so I called the dealer and they said that it was the fuel pressure re-leaf valve on the common fuel rail so I replaced that and that did not do it. I blew the fuel lines replaced filters and 2 out of three of the pressure sensors just wondering if anyone has run into this before and what it might be if so. It will throttle all the way up when you first start it then will go down to like 1500 rpms and just stay there.

Hello MasseyF welcome to YT! Going the call in
approach as you found out is not a sure fire method. I
have never worked on a tractor or system like you have
but I have worked with codes in the automotive field
for years. The part you replaced is probably nearly the
last step in a troubleshooting list in the repair manual
associated with the code. So without you having went
through those steps that check the circuits that
connect to the sensor are getting the proper
parameters there is no way to tell you what you next
step should be. There could be a broken wire or bad
connection in those circuits and your old pressure
relief valve could be perfectly fine. There is a topic
section for Massey Ferguson here which you could try
posting this in but most posters here are not familiar
with those newer machines. You can find that section
by using the ..Jump to or Hop to.. drop down at the
bottom when viewing a post here. Lastly I would
recommend posting this in another forum where
people post that use the newer computer equipped
machines and post about these types of problems
almost daily. That is on a forum call New AgTalk in the
..Machinery Talk.. section, see link. However what I
said here will probably be part of what they reply
there.
New AgTalk

One other thing is here is a site to download a repair manual for $35. I have never used this site, looks like they have good reviews. A downloadable manual is not available from AGCO or I would have directed you there, the hard copy from them is $230.
Manual

I checked all the circuts were good and that is why I had gone to the sensors.

This guy in this linked post claimed the dealer had to
hook the computer up and clear the codes. Do you
have a manual? I wonder if there is a way to get in and
clear them without a pc. I do not even know if a battery
unhook will clear them.
Another post

I am a retired diesel truck tech. I know there are some codes that even after 'fixing' the problem that have
to be cleared out by the diagnostic computer. It is just part of the fault tree routine. Many codes point to
a part giving a faulty reading, but the part is not the actual problem (oxygen sensors are a great example!)
The true cause may only be found thru extensive diagnostics. With any fault there is a 'tree'(routine) to
follow. Each step leads to an A or a B result, and you follow that next path to C or D, etc. Sometimes step A
is hard and it is very tempting to skip to step C, but unless you're lucky, this is a mistake. Unfortunately,
you really need a diagnostic computer and a fault tree manual in hand to troubleshoot most problems. Mark

Thank you all for the pointers that totally fixed it.