Cel - p0420

[Royisme]

I had this CEL pop up this morning, and took it down to have the codes scanned and it turned out to be P0420. From what I can find with some google-fu, it looks like a few different things can trigger that CEL, from exhaust leaks, fried cat, or fried 02 sensor.

I haven't spent a ton of time under the truck since the light came on as the ground is pretty muddy right now, so I'm trying to squeeze in some shop time to look at it. I haven't done any driving that would merit physical damage to the cat, and I don't hear any rattling coming from it while driving. Would I? Or would I have to pull it out and give it a shake? I'll be checking for exhaust leaks and should I not find any, that just leaves the 02 sensor(s?) I take it.

From this code, should I be looking at a specific sensor or multiple sensors?

 

[downpour11]

I'd say o2 sensor. There are 2 by your cat, I just needed to replace one of mine. It was pretty dirty/burnt.

 

[LittleCaesar]

If the o2 sensor(s) have never been changed, then it(they) may the culprit. However, if the code comes back, then the PO420 is more than likely the cat. Depending on the ability of your code reader, you may be able to generate some emission data to further narrow down the problem.

This thread may be of some aid:
http://www.toyota-4runner.org/3rd-gen-t4rs/75277-god-i-hate-po420.html

 

[Royisme]

Thanks for the info guys! I know that both of these sensors are the ones that it rolled off the lot with, so I hold no reservations that they are causing problems. My gas mileage has been falling every tank for a few tanks now, and just hit 14... is this an indicator that it's the front one? Are there cleaners I can try to use on them to get it to work for a few more months possibly? Clutching at straws here, 160 is kind of rough right now, but so is 14 mpg and knowing something is wrong under the hood.

 

[shadow247]

Here is the FSM info on diagnosing the P0420.

 

[Doc2012]

Why would you want to get rid of 420?!?!?!?!

It's a great idea!!!!

:jump::snacker::biggrin2:

 

[Stick Figure]

Why would you want to get rid of 420?!?!?!?!

It's a great idea!!!!

:jump::snacker::biggrin2:

I would be more than happy to give away my 420........ code that is, the other I can't help you with.

First time it happened was the sensor, a year later and beyond I know its the cat ... i just keep a code scanner with me to make sure thats the code before i reset it after every time I get stuck in slow traffic for any length of time. I'm hoping eventually one of these cat thieves I always read about will steal mine so the insurance company can pick up the bill, but no such luck so far. lol

 

[MountainBiker]

I'm hoping eventually one of these cat thieves I always read about will steal mine so the insurance company can pick up the bill, but no such luck so far. lol

:drummer: Yeah, same here!

 

[shadow247]

If it turns out to be a bad cat, some members have had good luck with the Magna-flo universal Hi-flow.

http://www.toyota-4runner.org/3rd-gen-t4rs/92911-new-cat-big-gas-milage-gains.html

 

[CitadelBlue]

OK .. My '02 4Runner with 141000 miles has the check engine, VSC off, and VSC Trac lights on. Advanced Auto check results in a P0420 code. AT 92000 miles (4 years ago) I had a P1135 (AF RatioSensor) code and replaced the O2 sensor in front of the catalytic converter.

Looking for suggestions/solutions to fix this ???

Thanks

 

[agloukhoff]

OK .. My '02 4Runner with 141000 miles has the check engine, VSC off, and VSC Trac lights on. Advanced Auto check results in a P0420 code. AT 92000 miles (4 years ago) I had a P1135 (AF RatioSensor) code and replaced the O2 sensor in front of the catalytic converter.

Looking for suggestions/solutions to fix this ???

Thanks

Am I reading right that you last replaced the O2 sensor 4 years ago?

If so, do it again. 4 years is short, but not unheard of for an O2 sensor lifespan.

 

[CitadelBlue]

Am I reading right that you last replaced the O2 sensor 4 years ago?

If so, do it again. 4 years is short, but not unheard of for an O2 sensor lifespan.

Not sure I explained it right. At 92000 miles (4 years ago) I had a P1135 (AF RatioSensor) code and replaced the AF RatioSensor in front of the catalytic converter not the O2 sensor ....

 

[agloukhoff]

If you have not replaced the O2 sensor - then replace the O2 sensor.

Make sure you get the right one for your car. You need different sensor for a 5speed and CA emissions car.

Use the list at URD:
Oxygen / AFR Sensors - Underdog Racing Development

 

[CitadelBlue]

I'm in northern VA , I have automatic and no CA emissions. Just looked under the 4Runner. Seems I have 2 sensors. One before the CAT with 2 bolts that hold it in place and one after the CAT that screws in like a spark plug. Is there another somewhere? Can I assume the front one is the Air/Fuel Sensor Denso part number 234-9002 and the rear is the O2 Sensor Denso 234-4622? and I need the rear one?

 

[agloukhoff]

Correct. Rear is what you need.

Personally, if I were you, I'd do front and rear.

The front 'should' help get your slightly better MPG if it's getting old. Plus often if one goes, the other follows soon after as they are both exposed to the same conditions.

Also buy from Amazon or RockAuto - URD charges way too much imo.

 

[CitadelBlue]

Any chance it could be a "not tightened down" gas cap? I had just gotten gas and had driven about 2 miles when the dash board lite up?

Also any + / - RE: sparkplugs.com for these parts?

 

[nissanh]

Thanks for the info guys! I know that both of these sensors are the ones that it rolled off the lot with, so I hold no reservations that they are causing problems. My gas mileage has been falling every tank for a few tanks now, and just hit 14... is this an indicator that it's the front one? Are there cleaners I can try to use on them to get it to work for a few more months possibly? Clutching at straws here, 160 is kind of rough right now, but so is 14 mpg and knowing something is wrong under the hood.

I got no CEL codes..... but I think my O2 sensors are the one came with the truck from the day 1. Can these lead to low MPG? truck has 182 K miles.

If it is the case, do I have to replace both sensors or one? which one?

thanks

 

[CitadelBlue]

Any chance it could be a "not tightened down" gas cap? I had just gotten gas and had driven about 2 miles when the dash board lite up?

Also any + / - RE: sparkplugs.com for these parts?

Actually Sparkplug.com price is higher so AMAZON here I come....

 

[TheDurk]

I got no CEL codes..... but I think my O2 sensors are the one came with the truck from the day 1. Can these lead to low MPG? truck has 182 K miles.

If it is the case, do I have to replace both sensors or one? which one?

thanks

The front sensor can definitely lead to degraded mpg and other performance issues when past 80k or so even with no CEL. The rear has no effect on performance and serves only to set codes.

 

[CitadelBlue]

Seems I received several solutions including replacing the front and rear sensors (about $100 each) and or CAT ($300-?) ... ...but the REAL solution was to remove the gas cap .. then tighten down until I heard a few clicks, disconnect the negative side of the battery to reset the computer ...... and all is well......