Allison 6sp: Codes, No Gears

[8100 Power]

Friend of mine called me this morning with his 06 LBZ not going into gear.

I pulled the codes for him and come up with these:

P0751
P0843
P0401
P0700

After clearing them everything was fine. Any ideas?

 

[dmaxfireman]

Friend of mine called me this morning with his 06 LBZ not going into gear.

I pulled the codes for him and come up with these:

P0751 - Shift Solenoid (SS) 1 Valve Performance - Stuck Off
P0843 - Pressure Switch C Circuit High
P0401 - Exhaust Gas Recirculation (EGR) Flow Insufficient
P0700 - Transmission Control Module (TCM) Requested MIL Illumination

After clearing them everything was fine. Any ideas?

whats done to the truck?

 

[8100 Power]

whats done to the truck?

4" Turbo back and a small 90HP EFILive tune.

 

[Mike L.]

Usualy the P0843 which is an electrical code will set off the P0751 code which a mechanical code ( stuck valve in vb ). Pressure switch manifold on the vb senses if the valves move to their position by way of ground pressure sensors. Either a valve stuck or you have an elctrical problem to the psm and it cannot sense that the valve moved to the proper position. Could also be a bad psm or loss of pump prime if it happened right after start up.

 

[8100 Power]

Thank Mike, I'll relay the message to him. So far it hasn't done it anymore since this morning. This is only the second time in the past year.

 

[ohkyguy]

06 GMC 3500 allison in limp mode

I have a 2006 GMC 3500. My tranny is rebuilt using a Suncoast GMAX6pac and has a ml converter. I also have ml tranny cooler.

It has been going into limp mode as soon as I start it up when it is cold outside. I have tried to start it up and let it set running to warm it up and when I go get in it the check engine light is on and stuck in third gear. I can go ahead and get it to drive and I try shutting my truck down and restarting several times and using my programmer to clear the codes and I can get it to drive fine and later on the codes clear themselves.

I am thinking it is just electrical because I noticed my batteries are very weak here lately.
I am getting the following codes po751,po843,po873,po877 and po700.

Any ideas?
Thanks
Bobby