okay , so my car was running fine. A couple of days ago i had check engine light and upon scanning found out that oxygen sensor needs replacement. The car was running fine though. So i had my oxygen sensor changed. After that change the engine is not turning on, it is ready and is driving on battery fine but the engine is not turning on and on dash 3 lights appearing VSC , ( ! ) (yellow color break light with exclamation) , Red triangle with exclamation . these 3 lights (image attached) are on and on MFD red car with triangle on upper left corner appears and it says problem when starting the car. All happened after replacing the oxygen sensor , the mechanic did try to turn on the car with the previous sensor also but no luck. PS did try to reset everything by disconnecting the connectors on the 12V battery for 10-15 minutes
You've mentioned that lights came on and error code pointed you to oxygen sensor... But then engine wouldn't start and "mechanic did try to turn on the car with the previous sensor also but no luck." So what are the error codes at this stage of the mechanics work and what did they recommend? Is it possible that starting the engine so many times when it wouldn't start has worn down the Hybrid battery pact that performs that work and you need to charge the hybrid battery before engine will start?
So the obvious thing for both these cases (even though the OP is probably long gone) is to read the codes that are obviously there. If you don't find any codes, then your scanner/reader is not good enough. Possibly it can only read the engine ECM and maybe the ABS/VSC/TRAC ECU and/or the SRS ECU. Once you have the codes and share them here, we can be of much more help.