I have a 97 528i with 150k miles on it (E39). I keep getting the code for Catalyst efficiency below threshold,Cyl #1-3 and a check engine light. Do I have a fried catalytic converter. It passed the Pennsylvania emmision testing.....any ideas?

my 140K mile 97 528i was in need of the fore and aft cat o2 sensors

changed them out reset the mil and she has run buttery smooth for 10 months w/out a mil.

o2 sensors can be had for $85 on the web.

installation will require an offset ratchet driven o2 sensor socket. i paid $22 for mine on the web

good luck