According to Alldata for 2001 8.1/Allison code P0700 is a transmission MIL light request and P0847 is pressure switch manifold shift valve D problem.

Brian41 I really appreciate the help. Seems like the P0700 will just come on everytime any other code comes up. Today I'll try and find a valve d manifold pressure switch, change it and I'm sure that will cure it. Just wondering what is alldata? is that for any vehicle?

You are correct about the 700 code, it is just sent to turn on the light letting you know there is a trans code.

Alldata is a automotive information program on DVD we used when we still work on cars, I kept it because I still own cars.

Your welcome Brian

PM me your VIN number and I will check for programming updates that you may need.

Will do, I'll get the VIN tomorrow as it's the soonest I can.

I had a 2001 2500HD with an 8.1 and Allison 5speed.

I had the the same light come on once and the tranny was acting wierd. Delayed going into gear, reved then kicked hard into gear, would not switch gears, etc. Turned the truck off and trans was back to normal, but the service engine soon light was on. It ended up being the Nuetral Safety/Back up switch module. My dealer said that it was a common part to fail.

My neutral safety switch went bad also but all it affected was the cruise control.

if you have a remote start and if the wire for the trans pcm was not connected it will throw a trans code...

replace the neutral safety switch that mounts on the outside of the trans on the shift shaft,,,the original is black and the new updated one is grey and you should be all set...Iam a Trans guy at a Gm chevy shop and thats about the only thing that fails on that trans..

true,,when you remote start the truck the ecm gets 12v but NOT the shift solenoids..
the trans shift solenoids gets 12v from the ignition switch so depending on how the aftermarket remote is wired you could see stored codes when you scan data..
electric codes like po758..po756