Sometimes a bad sensor will disable the ecu , so when you replace it , it will still not recognize, I would use ISTA+ to fix this, you might get lucky an due able to unhook the battery and get it to come back up, or maybe use a scanner like a AUTEL to re calibrate it, all that being said you could have bigger issues like a ECU swap, I had this on my e60 after the swap .
Sometimes a bad sensor will disable the ecu , so when you replace it , it will still not recognize, I would use ISTA+ to fix this, you might get lucky an due able to unhook the battery and get it to come back up, or maybe use a scanner like a AUTEL to re calibrate it, all that being said you could have bigger issues like a ECU swap, I had this on my e60 after the swap .