Bang

I had a P0420 that kept presenting and I thought I had it licked with a new O2 sensor. We're talking many thousands of miles. 10,000+

Now I only get it when I drive for prolonged periods at slow speed. The time it flagged before I was driving around scouting a campground maybe for about an hour at probably 15-25. All 2WD. I cleared that one.

A few weekends ago I took it up to a buddy's cabin and it's a pretty long dirt/gravel road. I was alone so I took my time, again maybe 20-30. It flagged again. I put it in locked 4WD when I get off pavement just to get the juices flowing. I have not cleared it since and it has not cleared itself after a few weeks of normal, on-road driving. Maybe 300-400 miles including some highway runs and typical around town stuff. Lots of motor starts.

I really don't know what this could be. I'd love to find it and fix it but I could just clear it when it happens I guess. Smog inspections are not an issue here.

It runs just fine all the time.

1999 4Runner Limited 4x4. About 270K on the chassis. Salvage motor has maybe 180K on it.

Malcolm99

What 02 sensors and part numbers did you put in, is your rig Fed emissions single cat?, is the cat original or aftermarket, is there any exhaust leaks between the manifold and last O2 sensor, what is your LT & ST fuel trims doing, and what is the ECU temp measurements(not the dash signal temp).

It' most likely either a bad O2, Cat, MAF, Temp sensor, or misfire, any problems here could flag the p0420

Bang

I really appreciate the help.

It is a CA with 2 Cats. They are original.

There are no exhaust leaks that I can hear or any shop has told me about.

I only replaced the first (front) sensor. I used a Denso 234-4153 Oxygen Sensor (Air and Fuel Ratio Sensor). I suppose I should change the second one too. I will order one like now. It's got 280K on it.

I took a video of my reader on a short drive from a warm start, city traffic, highway at speed, offramp and parked.

I assume ECU temp is ETC (°F) on my reader. It stayed between 190 and 194.

SHRTFT1 (%) would swing pretty good from negative (coasting) to positive (driving more slowly)
LONGFT1 (%) pretty much stuck at 0.8 cruising going to maybe 3.1 slowing down

I need a better reader. This one is pretty much the cheapest I could find for clearing codes.

Bang

Toyota 89465-49135Oxygen Sensor

1998-2001 Toyota 4Runner 8946549135
Toyota 89465-49135 Oxygen Sensor

Part Description
Sensor, Oxygen
CALIFORNIA SPEC
Part Name Code
89465
Manufacturer
Toyota

???

Malcolm99

That Denso 234-4153 is for the rear O2, my Fed emissions uses x2 denso 234-4162, you need the more expensive A/F Ratio sensor for the upstream, sounds like your fuel trims are good, not sure of the logic on that system when a CEL pops up, mine locks the fuel trims to 0% if either O2 fails. You need denso 234-9002 if it’s an automatic 9003 for standard transmission. I could see the p0420 being flagged if the Fuel trims cannot respond or not seeing what it wants to see at the upstream & downstream sensors. I’d put the -4153 in the rear since it’s new and the 9002 in the front, they do work in unison so it is ideal to have 2 new ones anyways but either way you need denso 234-9002, these trucks like the denso. Double check Amazon reviews for other 4R reviews but pretty sure I’m pointing you in the right direction. Your ECT looks perfect and the fuel trims almost to perfect with a p0420, I would expect them to hover around +/- 3% ST if all is well. Hopefully your cats are not being flooded with fuel, been waiting on an OEM Toyota Fed emissions cat for 2 months now world wide shortage due to thefts. $1600 plus 13% tax

Bang

Wow. I can't believe I screwed that up. Local AutoZone has that Denso part (a little cheaper than toyotapartsdeal, remarkably) and their web site also confirms I put the 234-4153 sensor in the wrong hole. Going to swap these today.

Bang

Just put a 234-9002 in front and 234-4153 to the back, cleared the code, now I wait.

I really do not know what happened before. I have only one historical order email and that was for a Denso 234-4153 Oxygen Sensor. But the only one I have replaced is the front and that has a short pigtail and the part number off it is, I think, 192400-8010 which looks like it's for a 2000+ Tacoma. Anyway I think they are correct now. Hopefully that fixes it.

Thanks again.

Bang

Update. Runs fine. Got another P0420 when I took it on the beach at Hatteras so it's still flagging going slowly over extended periods. No idea how to diagnose that. I think I'll live with it. No more smog tests here in this part of Tennessee to worry about.

If someone has a recommendation for an OBDII scanner that will give the numbers I need I can find some wheeling to do around here somewhere.

Blurm

Hey Bang, I am having the same P0420 code and it sounds like replacing the 02 sensor solved you issue ? Or did you end up replacing the cat ?

Bang

I never solved it. I decided to just live with it.

It became moot.



I didn't do it.
Now: 2016 Trail Premium 110K miles.

Malcolm99

The scangauge II will provide live data display that can be mounted permanently. It will tell you the fuel trims so you can see if the ECU is compensating, the ECU will adjust fuel trims to zero, constantly adjusting short term fuel trims at different loads as it learns to zero out long term fuel trims satisfying the O2 sensors, it also uses the front ECT, MAF, TPS, ignition & timing inputs to be the most efficient. A cat that has been saturated with fuel may lose its efficiency and most non OEM cats will never last long on a Toyota or work at all outta the box.