Have an odd issue with my 05 rx8
Most of the time I get in the car and start it with no issues. But at random it has been either starting with every light on the dash on and none of the gauges working. Or it won't start and flashes the immobiliser symbol. Other times it works great with neither issue. I changed the battery yesterday to make sure that isn't an issue. But I am wondering if it is a ground issue somewhere causing it. Any ideas?

 

sounds like a loose or corroded battery terminal. they suck so you might want to change them

 

The terminals on it are new as well. Such an odd issue, although electrical issues are rarely easy to diagnose

 

Update: Every time this happens it throws these same codes
U0121 Communication error to ABS HU/CM
U0155 Communication error to instrument cluster
U0167 Communication error to keyless control module
I just have one black key for it with no keyless remote