BMW 2002 z3 multiple warning lights on can turn car off they'll go off except service engine light is always on.The others come on shortly after running DSC,brake,ck engine,and one other.Then it's low on power .

Do you have your battery lights coming on in red? It kinda sounds like your alternator isn't charging. See you can read out the engine codes any local auto parts store should have one to lend you for free if you dont have one.

No the battery is up and holding at 12.9volts.

WELL every time you cycle the ignition it rescans all the computers, so for them to come back on so quick means, yes low voltage, just as much as a BAD COMMON GROUND can do that, have been a European car specialist for 5 years now, extensive BMW models, including both of my own. feel free to scan the car to find the codes and confirm the reasons are all related.napa, auto zone, etc. all scan for free.and let me know

Is that battery voltage with the vehicle running? Also do check to see what your AC voltage going to the battery is. When you say the vehicle looses power, do mean if you press the accelerator it wont rev up or more move or does it just feel like it has less get up and go? Still do pull codes when you get a chance.

I had random lights coming on in my 2.8 Z3 and engine power loss problems, especially pulling away from a start. Eventually found out the battery was old and not holding charge and dropping way below 12V when starting the engine. Installed a new battery and now all random light problems and engine power problems solved. I think the low voltage at start up was playing havoc with the engine management system.

most these cars have a problem if you go below 12v for any reason...