JimiJams

Hey, I've been getting a p0420 code for the past few months and just took my emissions test and the guy caught that. I was thinking of starting cheap and just replacing the front o2 sensor but I think I just ordered the wrong one. I have an 00 4runner with 2 cats. Does that mean it's a california emissions model? If so I just ordered the wrong sensor...

FogRunner

In 2000 Toyota made the 4runner 50 states legal AKA Calif emissions which is noted by the two cat converters. The O2 sensors Calif emissions are about twice what a federal emissions 4runner costs.

FOG

JimiJams

so I am gonna have to get the california emissions version then right?

TheDurk

A P0420 is more probably the rear sensor although it could be the front. Usually you will get other codes first if it is the front.

2001 was the first year for two-cat systems in all 50 states. 2000 was still California two-cats and 49-state one cat.

So you need the Cali. wideband Air/Fuel Sensor in the front (Bank 1 Sensor 1). In 2000, they are different for manual/auto and 2WD/4WD (mainly wire length, I believe). In the rear, it is a normal O2 sensor. Go here URD O2 Sensors to get the correct Denso Part number. Then buy the sensor from URD, Amazon, or wherever you find the best deal using that number.

JimiJams

OK maybe I'll try replacing the rear sensor first and see what happens. I just hope I don't have to replace the cat$.

PismoJoe

I have to disagree with thedurk here..

I have really never seen the rear sensor go out, the front one is almost always the culprit.

Indian, move to CA and see what they say about that lol

TheDurk

Not when it's P0420. (Catalyst below efficiency.) The ONLY purpose of the rear sensor is to set that code. I had to change my rear sensor at 90K to cure my P0420. In most cases where it's a solo p0420, the front sensor has already been done, so doing the rear is the obvious thing to do.

If the front is 80k plus, you probably end up doing both. It would help to know the miles on these sensors.

PismoJoe

I didn't mean in this case for that code, youre right about the sensor, I just meant usually the front goes out before the back does.

JimiJams

There's 89000 miles on the truck and neither of the O2 sensors have ever been changed. They may both have to be changed. I know they recommend changing them at 80k but I thought I'd wait for the sensors to throw a code which they haven't yet. And I know when the O2 sensor code gets thrown it's usually for the front sensor. So assuming the front sensors still good it probably makes sense to replace the rear one first in this situation and see if the cel stays off. I like the idea of starting with the cheaper sensor too

JimiJams

...and not to sound like a complete idiot but the rear cat has holes in the outside cover right? Whereas the front cat has a solid cover with no holes. Just wanna make sure I'm dealing with two cats here.

TheDurk

I totally agree--never meant to imply otherwise.

JimiJams

bump...so just to clarify 1)I do need the calif emissions O2 sensor for the front
and 2) the rear cat has a heat shield with holes rather than being all solid like the front right? stupid question I know, just making sure there's definitely 2 cats here.