wyoming9

iTrader: (1)

Knowing what the code is and understanding how it works is no big deal

The issue I have is that it is random . As far as I can figure there is no set pattern tripping the MIL.

2000 3.4 replaced the down stream sensor a few thousand miles ago. Like last month.

It trips I read the code one needs at least a code reader with these engines

I clear the code good for another couple weeks most trips are either short like 10 miles or a few hundred.

Go figure.

wyoming9

iTrader: (1)

Here I am another 2500 miles So far so good.

Weather has been from rain to cooler temps at night .

Maybe that bottle of Stargon in the gas did something.

Time will tell

HighLux

What brand rear o2 you use?

wyoming9

iTrader: (1)

Denso from my Toyota dealer.

They were the best price

wyoming9

iTrader: (1)

The other morning it was around 35 to 40 degrees The truck lives in a Garage .

It had been fine for a few weeks.

I pulled it outside around 0330 hours as I was going out the door the phone rang call took about 8 minutes .

So it might have idled about 10 minutes.

Drove about 5 miles MIL is on. No good place to pull over for about 15 miles .

Read and clear the code drive the rest of the day 200 plus miles good to go

This is driving me crazy!!

wyoming9

iTrader: (1)

I can only think it is a ECM glitch that causes it to trip at random times .

I guess time to buy a new one.

Then i might have good luck the first time in my life get it past emissions and be good for another year.

oldblue

i would say its most likely that catalyst starting to fail. at certain times i guess its not cleaning the emissions as well as it should and the rear o2 picks up on it.

wyoming9

iTrader: (1)

Well if I get only around 10,000 miles to the converters they will cost more per mile then gas.

A toss up really new ECM or the 2 Cats be about the same price.

Go figure exhaust gasket leak before the O2 sensor of course that does not trip the MIL story of my life.

oldblue

if those are aftermarket converters, then yes that's about all you will get out of them. the cheap aftermarket converters are good for a year, maybe two, then the stuff on the inside stops working like it should. i've been through several on my truck. but if you have an exhaust leak, you need to fix that first because that can cause a false code to trip.

ARB1977

Or save some money and gut the down stream cat and run an o2 sim from URD. Keeps the light from coming back on.

250000_yota

Wyoming, you never did mention whether you used an OEM cat or not, but if is is aftermarket, I have to agree with these guys. We see someone come in once a week or so at the dealer who had the exact same issue as you. Got a p0420, cheaper out and bought an aftermarket. Then when it trips the same code again, they go back, but the shop shrugs their shoulders and tell them to come to us.

There's a reason toyota cats cost so much. Their worth it.

wyoming9

iTrader: (1)

That is the trouble both are from Toyota.

I have a good relationship with my parts manager I wonder if they are out sourcing the cats and selling them as Toyota doubtful??

I had gone with Walker but when I need to replace the exhaust system I went with the Toyota ones.

** Exhaust leak was fixed as soon as I got back home.

I was remarking that Did Not Cause the MIL to trip after a 100 miles of leaky exhaust just in front of the O2 sensor.

wyoming9

iTrader: (1)

I think I may have found the problem.

A small hairline crack in the cat that could not be seen because of the heat shield.

That expanded only after it got real hot under heavy load.

Get back to the shop unload things by then it was cooled off and closed up.

I guess it can`t hurt to weld it.

I mean pay close to $2000.00 for 2 converters on a $3000.00 Truck

Maybe I could Like rent them out for emission inspections