I've been working on my truck for two weekends now with no success clearing P0700, P0750 5.7L (191,000 miles). I had no codes until the transmission went into limp mode. I could get out of limp mode by turning off the truck and restart. it did this twice on my way home from work. When I did my first OBDII scan it said that I had under voltage and valve power feed failure, and P0700 code. so I replaced the computer from Flagship One first. I drove it to work after install and no codes or limp mode (50 minute drive). On the way home it went into limp mode. I had code P0700 and I probed the solenoid pack from the computer harness connection. So, I replaced the solenoid pack, both filters and new transmission fluid. I test drove it got the check engine light after half a mile and in limp mode. I checked fluid at the store parking lot when it was hot and needed to add about over a quart. Added fluid and cleared codes and drove home and got limp mode within a few minutes again. The scan still showed P0700 but now P0750 this time. So, just to be sure I checked the new solenoid and wiring again from the connector at the computer and all checked about 2.1 - 2.2 ohms. I'm at a lost of what to do next. any help would be appreciated.

 

Bad wire inside the transmission or bad computer

 

Fjdavid, Did you find a solution?

 

He did mention using another solenoid pack & PCM ...

 

So, on ours.. We took to dodge dealer for airbag replacement appointment. told them bags, nothing else. they call wanting to do other stuff,, LoL NO! .. Drove truck home, another day to work.. next morning Transmission is ****ed,, no drive. Towed to shop down the street, Bad trans! (smoke was coming from dip stick) they put in new rebuild trans... Now a few thousand miles later, we get limp home mode. turn key off restart, good.. then limp home. Shop said it was TIPM.. there is new firmware might take. might kill TIPM.. So, disconnect batt.. works for a time,, then back.. after a year we put in new TIPM.. Now it goes into limp home without CEL.. guess thats dodges fix. .. Been living with for a few years now, Two speed manual power glide... But started stalling going into drive, or random from stop, put factory TIPM in,, same.... Took to another trans place, they said it needed to be programmed to learn shifts??? Hey, working great with stock TIPM .. month later.. Same... < Time for trade in ??? Oh, and getting messages the passengers side airbag needs replaced WTF??? thought they did our bags..... sad, just sad

 

Ooh Geeze it sounds like a ton of issues are going on with these Cummins models.