Lex*Toy

Throwing a CEL P0420, Bank 1after about 300 miles (gradual). Searched here and found a couple of VVT-i's 1UZFE doing the same, but there was debate about whether it was before or after cat O2 replacement.

I just want to replace the the sensor and not go throught the hassle of having someone check the voltage.

I reluctantly have 1 Walker O2 sensor (before cat) on the Drivers Side and the rest are OEM Denso. It was fine for over 4 months.

So the debate still continues, is the problematic sensor (Bank 1) in the headers or after the cat?


Note: I have SS Headers install, and full exhuast system with high-flow cats. (Cats tested good at emission 2 months ago)

O. L. T.

iTrader: (17)

It is usually the cat itself rather than the sensor. The only way to know for SURE is to check the voltage at the sensors to make sure they are fluctuating properly between 2v and 8 v. if one is not, it's a bad sensor. if they are both right it is a cat. There is NO other way.

Here you can see my BS 1.1 and BS 1.2 (bank sensor 1 and two) as well as my BS2 reading proper voltage as I was testing my code which is the same as yours. turned out to be a bad cat. without this reading you have no way of knowing.

O. L. T.

iTrader: (17)

Here's the code guide

Lex*Toy

What is meant by "Bank 1" or "Bank 2"?

O. L. T.

iTrader: (17)

bank 1 is cyls 1-3 and bank 2 is cyl 4-6

jgscott

iTrader: (1)

He mentioned a 1UZFE. So he has a SC400 I guess. I think what he wants to know is if Bank 1 is the pass side or drivers side. And is the code CEL P0420 the pass side or drivers, and is it the Sensor in the Manifold ( Front ) or Near the Cat Rear.

Also got to be more that 6 cyl's.

O. L. T.

iTrader: (17)

one would tend to add a cyl to each bank if the situation need be.. Anyone short of the village idiot can pull "bank 1 = first set of cyls" from that example

jgscott

iTrader: (1)

And ........

I think what he wants to know is if Bank 1 is the pass side or drivers side. And is the code CEL P0420 the pass side or drivers, and is it the Sensor in the Manifold ( Front ) or Near the Cat Rear.

Lex*Toy

Thanks OLT for the info.

I recently had the cats checked, where they passed beyond margin. This leads me to believe that their is most likely a fault in the sensors.

I understand your diagrams and checking the voltage, where I am merely looking for a starting point for pinpointing the issue.

As such, the simple version of what jgscott would be useful (i.e) Bank 1- Drivers Side, etc.

There are also threads on this site that suggest only the post-cats sensor could render such a code (P0420) since they are the ones reading the O2 after running (when code occurred)....

Is any of this true?

pr0vakativ

what is the desciption of the code p0420? is it catylist converter low effidiency?the post cat O2's rarely go bad. u have to check if the rear is switching if it switching like the O2's before the cat u have a bad catylist converter and need replacing. if the voltage of the front O2 is not switching but going at a steady voltage then the pre cat O2 is bad replace it.

so basically if the post cat O2 is switching means bad CAT
front O2 not switching but steady voltage replace the pre cat O2 sensor

Oh yeah bank 1 is the side where #1 cylinder is and toyotas are always passenger side

O. L. T.

iTrader: (17)

yes. generally it throws a more specific code if it is a sensor. not always

Jonathan o

Are you using oem(lexus) cats?

Lex*Toy

No, aftermarket High-Flow Cats.

Jonathan o

Ok! that is the problem. I had the same dilema a few months back with my 99sc4. Your hi-flow cats will never meet lexus settings. But there is a solution to your problem check with this guys.
"www.casperselectronics.com ". Look for part#104057. Don't waist your money on the o2 sensors that wont fix you problem. Look at the info and post back with your results. It work for me.