As I recall in being under there, it sounded kinda rattly when I banged on it. Trucks at 170k almost. Most likely on the original cat. I'm just fearful that if I change out the cat, which I can imagine is going to be costly, that I'm still going to have an issue. Is there anyway to diagnose if that B1S3 O2 sensor is faulty aside from replacement? Additionally do you have a recommendation on a replacement catalyst?

 

Whenever I reset the code/s the fuel mileage is restored until the code tips off again.

 

Lesmyer made a good point in the thread that he deleted. When certain DTC's are set, they can cause the PCM to disable the TCC solenoid in the transmission. I'd have to do some research if P0420 is one of them. Off the top of my head, I'd say there's a good chance of it. You can test the theory by holding a steady 55mph, then very lightly apply the brakes with your other foot, just enough to turn the stop lights on. The RPM should increase ~100.

 

I changed out S1B3 sensor and my voltage wavelengths are fluctuating *less*, and thus far thru about 2 hours of run time its not throwing the light anymore.

 

Couldn't find in my factory shop manual where the P0420 set actions included the TCC but I believe I have read somewhere the TCC is one of the typical things that is affected when codes are set. Because I could not find the info is why I deleted my original post. OP could monitor TCC slip with Torque app. I have done this before when investigating my poor mileage.

 

You can check to see if the converter monitor is complete. If it's not, you can perform a drive cycle which will force the monitor to run and complete it's tests. Even if there IS a problem, the SES light will not come on until the monitor runs, completes, and detects a failure.

 

It coded again; and Capt. Hook when cruising at 55 and doing your test my RPMs do infact raise about 100 RPM. What does that mean?

I'm going to try one of those O2 spacers of Ebay for the immediate future. I cannot afford a converter right now, nor can I afford 12 mpg when the PO420 code throws.

However any analysis about the TCC would be appreciated.

 

It means your TCC appears to be engaging.

 

Uh news flash.........those spacers aren't gonna fix your problem!!!the pcm randomly runs a test to check the catylist efficiency via your secondary 02 sensor..., putting a 'spacer ' between the exhaust pipe and 02 sensor will do nothing for u....it's not gonna fix your issue, my money is on your converter being plugged........although u may wanna check your wiring going to the secondary sensor for any damagedo a google search on p0420 , u will find the syptoms related to the code, and the conditions that are met to set the code in your pcm.....

 

Did you ever check fuel pressure and leakdown?