Yeah don't mess around replace them all. Buy your O2 sensors from Atlantic British or make sure they are made for Discos not those universal ones. Go to harbor freight and buy a cheap scanner that way you can erase your codes and read them yourself.

 

.....ok changed both o2's and now after a 3 hour trip. another code pops up---could it be the cat???

p0430???

 

Read the codes again and see. I actually had a bad new O2 sensor.