Catalyst Monitor and Drive Cycles
 

So I've known my catalytic converters are kinda dying. I've got a bank 2 code a few times, but only when the car is idling in traffic. I observed the O2 voltages and they show the bank 2 cat is not very responsive. But I haven't been driving in traffic for a while, and haven't had that code for a few months.

Anyway, couple months ago, I looked at the Readiness Monitors, which were all Complete, including the Catalyst. After that, I got some random Secondary Air Injection codes, so I cleared them. So the IM monitors were reset too. Now my smog is due, and I've been driving the car like I how I normally use it (mixed on local and highway driving, cruising at 80mph, etc.). All the monitors have set, except for Catalyst, and it's been almost two months and more than 1000 miles, and it still won't set. There were no codes set during this entire time.

Does anyone know the drive cycles to get all monitors set so that I could get my smog done?

In CT we only need 4 out of the 5 to be set to pass. Do you need all of them set?

I'm pretty sure (from other cars) secondary o2s are tested at 60mph for greater than 1 minute.

I remember reading from a post on here and somewhere on the Internet that all have to be set for CA. I've read about the drive cycles of some Mercedes Benz's, and they mention driving at 50 mph without changing the load for more than 10 minutes.

I'm in the same situation, with the P420 code.

I think the first test would be to swap O2 sensors between the 2 banks to verify that its just not failing O2 sensors.

If so then its a cheap fix.

I did have the engine light go out for a few weeks and then it came back on so it must be borderline.

I just want to get through my Nov smog so I have another 2 years to consider options.

There is a universal Magnaflow Catalytic converter (~$190) to weld on but it would have to be after the header and have O2 bungs welded in as well and remove the 2nd cats to make room. Probably would not pass a visual inspection during smog testing.

The new headers would be ~$1800 each side as a last resort.

So my car finally set the Catalyst monitor to Ready/Complete. All the other ones have set a long time ago, even O2 and HO2.

I was reading about drive cycles, and found a couple for 996 and 993. I figured this car might just use the same cycle. So I loosely followed that cycle, but the two things I did different than before were: I let the car idle for a few minutes before driving it, and I tried to cruise at 55 mph on the freeway (which was scary because even though I was in the right most lane, people were still coming up to me pretty fast, then changed lane to pass.

Just want to share my experience for those who want to get their car smog ready fast.

Here is a nice write up on catalytic converters.

The Misleading Nature of the PO42O Code - Eastern Manufacturing

There is no direct measurement of the catalytic converter health, instead it is a diagnotsic run by your car's computer. As this article shows, there may be several factors contributing to setting this code.

Excellent article on cat's. I had to read it twice. Thank you Jamesp.