ecu problems

well last week my 06 2.2 auto cobalt died on the road. took it to dealer they said needs new ecu. along with tons of other stuff. well i drove it home it drove good but then next day nothing. ran scan p0601 i believe. ecu dead memory shot. so i towed it back this past Friday they put in new ecu. well it ran. drove it home and on the way home check engine light came on. scanned it and got p0315 crankshaft position variation not learned P0315 - Crankshaft Position System Variation Not Learned
Possible causes
- Crankshaft Position (CKP) sensor harness is open or shorted
- Crankshaft Position (CKP) sensor circuit poor electrical connection
- Faulty Crankshaft Position (CKP)
- Damaged crankshaft pulse wheel teeth
i suppose the wires or senor went bad. question could this cause the ecu to fail?
i don't see the crankshaft pulse wheel going bad being no sensor removal has occurred. don't even know where it is yet.

and if this sensor is bad and the engine is still ruining is it running on limp mode? and safe to use until i can replace the bad parts? where is the sensor located on this car? thanks bp.