This will be rambling but I'm trying to give as much information as I can:


The car is a 2006 roadster with 31000 mi . Due to my health issues The car has been sitting up for a little over a year. I would infrequently start it and let it run for a while sometimes driving it around the neighborhood. The other day it wouldn't start with a jump. I noticed the battery was well past due for replacement. I bought a new batter, installed it and took it out for a ride lasting about forty minutes not driving over forty miles an hour. It performed just fine, no issues. Yesterday I thought I'd go out for breakfast in it. It started fine and until I stopped at a red light all seemed well. When I took off from the light the car seemed to be in low gear, thought maybe I had accidently tapped the gear shift to first or second gear but it wouldn't up shift. I pulled over and put it in park and when I tried to put it back into drive the gear shift wouldn't budge. I shut the engine off and then restarted and it slid right into drive. I took off but with very low power and the spedo wasn't working. Made a U-turn and went home and parked it in the garage. This morning I went to start it and the dash lit up but engine would not start.


Any one have any thoughts on what could have happened?

 

Frist thing to do is check all your grounding points. Look at the cable itself , sometimes corrosion can build up inside the cable. Then at the connection on the fender well. Then to the engine. Pizzaguy has a checklist for using an amp meter to ensure proper grounding.

 

Sounds suspiciously like a transmission conductor plate to me.
No speedo ( speedo pickup is on conductor plate )
staying in low gear, refusing to shift ( limp mode )
It could just be low fluid, check the electrical connector front right side of tranny for leakage signs.

Now THAT sounds like an RCM ( Relay Control Module ) issue, assuming "would not start" means engine would not turn over.

 

Try and cut out the guess work and get any codes read.