Ok I have a 99 grand cherokee Laredo the tranny went bad so I replaced it. The tranny we installed was off a 2002 grand cherokee overland with 72k on it. The bone yard said they tested it and it worked perfect.... But now that's its in my jeep 1st gear and OD does not work... So we put it on the scanner and code P0700 keeps coming up after research I think I figured out its the TCM giving me problems so my question is can the dealer reformat the TCM that's in my jeep? Or can I just grab the TCM out of the overland that the new tranny came from and put it in my jeep, will that work? Or I found a company that sells TCM's and they program it for my jeep with my VIN then get the P/N off the TCM off the overland that the new tranny came from..

I'm really hoping that the dealer can just reprogram my TCM

Well thanks for your help guys!

 

Welcome to CF. I'm not sure if your '99 TCM can/should be reflashed to the '04 specs, or if you should try to get the '04 TCM and use it.

 

The transmission came out of a 2002, but if I install the 2002 TCM do you think it will be compatible with the computer?

 

Sorry, I meant '02.
Hard to say as a bunch of changes were made in the '00 model year.
Just thought you would be able to try the '02 TCM first, before spending money to go the other route.

 

P0700 is just an information DTC that the TCM sends to the PCM. Basically the DTC is telling you that there is a stored DTC in the TCM. It takes more than a simple code reader to scan TCM's. If you know someone with a higher end reader then that might help you out. It could be something simple like a TRS (trans range sensor) or speed sensor. Also if you haven't done it already, go ahead and check fuses just in case one might have blown during install or from last trans.

 

I do plan on going back to the bone yard and trying the TCM that goes with the tranny on tues. thank you for the help.

 

The other code that I got was P1768..

 

You seem to suspect the TCM which is possible. P1768 is for the TCM relay inop or "off", either a problem with the relay itself or the circuits to the relay causing the relay to not energize and send B+ to the TCM.

 

Any suggestions?
So being that I put a 2002 transmission in my 1999 do I need to get the TCM reprogrammed? Is it normal for people to reprogram there TCM after doing a tranny swap like I did or should the TCM work fine with the tranny that I installed?

 

All this discussion aside. I got a real queasy feeling when a boneyard says they "tested" a transmission.

 

There good people I've known them for years... They test it wile its on the lift before they tear it apart

 

Sorry, man. I'm not saying they're unreliable, I'm just going from past experiences. When I was a boy, junkers never washed and slept in their clothes. Times have changed for the better.

 

Hahahahahaha..... O I didn't take any offense to what ya said I'm not close to them or any thing I just been buying stuff from them for years and there always pretty reliable and very professional, it's insane how organized they are... But at the same time there the only bone yard I go to because the rest of them around are like what u said hahaha...

 

Do the basics first, check fuses like stated, fluid level is good when warm?

If the trans is good it should shift normally 1-3 when shifted manually. if it does its a TCM issue, either its the TCM its self. A relay, or a power issue. could be a fuse, a relay, a bad wire, something you left unplugged? just ideas to look into.

The relays should be interchangeable if its like my 2000, might try swapping ti with something you know works like a horn relay ect...

 

Got the new TCM and no luck any other ideas?