Transmission going to limp mode

2003 x type 2.5l 240,000klm, The car sits in Florida for seven months a year and is used for 5 months as we avoid the winter, upon arriving had a dead battery replaced that and thought all was good however transmission will go into limp mode the transmission light will come on and on the instrument panel the mileage/klm indicator goes to 0 and the actual speed needle also will go to 0.
If I am at speed when this happens there is a small clunk? I then will pull off to the side and shut the motor off for about 30seconds restart and everything is back to normal.
This can happen at any time I can drive several hundred klm with no problems and then when going out on a short run the problem will repeat?
I can be sitting at a light and the transmission light will come on and when moving from the light will have to get the rpm up to about 2000 before the car moves so I move to a safe location and shut off the motor for 30 secs. restart and everything is fine for a period of time.
I have been reading about low/high voltage causing a problem with the tcm so have checked my voltage and upon starting it is about 15V for a short time then drops down to 14.8 and eventually down to 13.5 and lower not sure if this is OK or not I think it is a little high?
I cant find anything on this site re this particular problem would appreciate any help.

Update:------ Took the car to a transmission shop, they indicated it was 2 wheel sensors which they changed: Did not resolve the problem. When I was driving and applying the brake the abs system kicked in and immediately the transmission went into limp mode, I pulled the abs fuse to remove the abs function and stop the pedal pulsing, and ordered an abs module from a wrecker, it has been installed for 5 days now and no issues also the cruise control is working again which is the fist in 3 years?
I may have no abs but everything else is working fine.
Upon further investigation we discovered that the tone rings or exciter rings (British and US terms) on the front right and rear left are no longer there, they have rusted away due to the salt on roads in winter in Canada.
I do not plan to replace them as this is a Florida driven car now.
Hope this helps someone