Greetings all- My '98 3.8L Windstar's check engine light is on and AutoZone read the code to be P0430 "catalytic system efficiency below threshold bank #2". If I understand correctly that means that the Oxygen sensor after the Cat is not reading enough of an improvement compared to the one before the Cat so it thinks the Cat is bad. I have a problem with this, not only because it would cost $3000+ to replace but also because it passes State tailpipe emissions testing with flying colors. Has anyone had this problem and how have they fixed it? I think I'm the trail of a solution and will let you know how it turns out, BUT FIRST.... Which is Bank 2? I'm guessing that Bank 1 is cylinders 1- 3 next to the firewall so Bank 2 would be 4-6 closest to the front of the van. Please help me out. Thanks in advance. -Jeff

It is also possible to have one or two bad O2 sensors on bank 2 giving you the same indication.   

Chuck- Aren't there codes for bad O2 sensors too? I have only the one code. Do you know which is bank 2? Thanks. -Jeff

There are codes for bad sensors, but your sensor may be giving an inaccurate/incorrect reading for the O2 going past it even when the computer thinks the sensor is still good.  This would allow your Windstar to pass the emmssions test even though you have a bad O2 sensor.  Best I remember Bank 2 is the back half of the engine, just don't have my book handy so I can check.  

Chuck- That's interesting; I don't know how much the dealer checked the O2 sensors when I had them look at it but their answer to my problem was replacement of the Cat ($3000+). If you get a chance could you please check your book to confirm which is bank 2. Thanks. -Jeff