Can bad (really bad) O2 sensors cause transmission fail safe mode?

NO an O2 sensor will not cause the tranny to go into limp mode. The tranny shop should scan the Tranny control module for fault codes. You can have bad speed sensors, bad solenoid bad tranny control module ect

Please check the o2 sensor manually, make sure it tight and in good connection. A bad connection may cause an error reading to it. If all good, then replace the o2 sensor. On some car with electronic control transmission, any fail to the engine may causing the computer to command the transmission to work only in some condition to avoid a higher damage. Beside the o2 sensor, please have check to the fuel pressure to have normal pressure that need to be injected. It could be the fuel pressure or the fuel rail that doesn't kept enough fuel in it to be ready to inject.

the 02 sensor has nothing to do with the transmission but it will mess up the running of the engine like fowl the plugs for example. i would say probably there,s a sensor on the transmission that,s at fault but the 02 sensor would,nt do that. if your having trouble with the shifting then it might be the filter in the transmission is starting to clog up.

Go to the dealer where they have a factory scanner that can read more than OBD II codes. They will scan the different sensors and road test the vehicle to see what and when the trans goes into fail safe. That will pin point the cause.

no, but it sure as hell will put the engine in fail safe mode if all your oxygen sensors are bad.