2001 VW Passat P0431/P0421 Catalyst problem

I have a 2001 Passat 2.8L V6 with 92,000 mile

Recently the Check Engine light went on with "Emissions Workshop" message. The dealer replaced the "Coolant Temp Sensor" for $200 and I got the diagnostic paper:
16502 P0118 035 Engine Coolant Temperature Circuit High
17831 P1423 035 Bank1, secondary air system air flow too low
17819 P1411 035 Bank2, secondary air system air flow too low

After a day, the Check Engine light was on again. Now the diagnostic says:
16815 P0431 035 Warm Up Catalyst, Bank2 Efficiency Below Threshold
16805 P0421 035 Warm Up Catalyst, Bank1 Efficiency Below Threshold

The dealer offered to change both converters (cat) for $3000.

This in insane, because the car is running perfectly, so it must be only a sensor problem or something other minor stuff (O2? thermostat?).

Search on this problem & you will see alot of people have it. How long did you run the car with the light on the first time? It seems those cats are fragile & will die easily, especially when run with a problem in the engine management system. 92K is more than the govn't makes VW warranty them for, so how much longer are they going to design them to last? The only other way (aside from the O2 info that the ECM uses) that I know how check them out is to use an infrared thermometer. While the car is running with cats good and hot the rear of the cat will be about 10% hotter than the front if it's working properly. If you are thinking of trying an aftermarket cat be sure you get a three-way catalist, two-ways are commonly sold since they are cheaper & may keep the check engine light off, but you will fail an emmissions test because of high NOx levels. You can find them cheaper aftermarket, yours are just now starting to be more available. Try a google search on "volkswagen passat catalytic". Here's one I saw:

http://catalog.autopartsgo.com/

You have to call for pricing, uh-oh... there's alot more VW parts place out there.

Hi guys,
I have a 2001 passat, 4 days ago the engine light came up, after I scaned it at the auto autozone place it came out with a "secondary air system "...... can you give some advise on what do I need to do ....since you said that the dealer is going to be too much money.....

Any help I will really appreciated....