NathanOfSeattle
Member
Got the P0420 error. I reset my CEL (by disconnecting the battery) and the light back back on with a P0420 error again. What should I do to fix this?
P0420 solutions?
- Thread starter NathanOfSeattle
- Start date
Register to hide this ad
PhdNPrerunners
New member
I have the same problem on mine. Check your o2 sensor after the cat, that's what's wrong with mine
NathanOfSeattle
Member
Did you mean to say, replace (I don't know how to check) the rear o2 sensor? Where exactly is it located?
Gotta get under your 4R. Its between the cat and the muffler.
01t4rnr
New member
all the info you can stand to read
http://www.google.com/search?hl=en&q=p0420+4runner+o2+sensor&aq=f&aqi=&aql=&oq=&gs_rfai=]
and yes it does sound like the sensor before the cat
http://www.google.com/search?hl=en&q=p0420+4runner+o2+sensor&aq=f&aqi=&aql=&oq=&gs_rfai=]
and yes it does sound like the sensor before the cat
NathanOfSeattle
Member
Thanks guys! Did more searching and people were suggesting either replacing the rear O2 sensor or both the rear O2 sensor and font O2 (A/F) sensor. Should I just replace both the O2 and A/F sensor at the same time since I'll be down there? My 4runner is 148,000 miles old and I don't know if the sensors have ever been placed.
BTW, I found the sensors on this site to be pretty decently priced. Are these the correct ones or should I go to the dealership for the parts?
Oxygen / AFR Sensors - Underdog Racing Development
BTW, I found the sensors on this site to be pretty decently priced. Are these the correct ones or should I go to the dealership for the parts?
Oxygen / AFR Sensors - Underdog Racing Development
PhdNPrerunners
New member
Get the part number off URD and then check amazon for a better price. I bought mine off amazon for half the price. Good luck
NathanOfSeattle
Member
Thanks! Amazon had them for cheaper.
Should I go with these aftermarket Denso O2 sensors or go to the dealership to get the "Toyota genuine" O2 sensors?
Jon
New member
The Denzo's will be sufficient, don't get ripped off. I have to do mine some time soon too. When you get the new o2 sensors and before installation take them to a parts store and get the 02 sensor socket. It's a must. Exhaust hardware is always stuborn to get out and a normal open ended wrench will more than likely round it off.
Good luck and don't forget to soak in PB Blaster!
Good luck and don't forget to soak in PB Blaster!
TheDurk
Elite Member
Only if you collect red boxes. The sensors are identical. This applies ONLY to DENSO sensors. If you only do one, p0420 is usually the rear--the ONLY purpose of the rear sensor is to set that code.
You may want to pick up some new nuts Part #90179-08059 at the dealer or any stainless M8-1.25 nuts should do. Don't forget copper anti-seize.
Last edited:
NathanOfSeattle
Member
Thank you! I might also do the front since I heard that could help improve gas mileage. My 4runner is 148,000 miles old and I have no idea if the front O2 sensor was ever changed.
Is the copper anti-seize the same as PB blaster?
TheDurk
Elite Member
No, they are very different. PB Blaster goes on the old stuck nuts to help get them loose. Anti-seize goes on the studs when you are putting the new nuts on so they have a hope of coming off easy the next time. I'll be able to tell you if it works in about two years when I'll be due for a third front sensor.(My original lasted 75K).
And yeah, the front O2 can improve the running of the engine and if you don't know its age you will be wondering at every code that gets thrown and every engine sputter you hear. They can degrade without throwing a code.
Last edited:
99Yotarunner
New member
its funny this thread got started, mine just kicked the light on yest for the same dam thing.....worst part i all ready did both the 02 sensor lil over year ago, no there giving me trouble again......might be that while off roading my exhaust flange gave out ans it was leaking for few days right befor the cat so after i got it fixed the light popped on day later.....so i cleared the codes thinking maybe since it was leaking ex then was fixed it trip the emissions rear o2 signal.........time will tell i guess
NathanOfSeattle
Member
Thanks you guys. I think I have enough collective information now to get started (hopefully this weekend). If after I change the sensors and the same code comes back, does this mean I will have to change my cat converter?
PhdNPrerunners
New member
It could be the cat or you could have an exhaust leak. I would have it checked before you spend the money on the cat. My exhaust is leaking right where the cat bolts up and that is what is throwing my check engine light on
NathanOfSeattle
Member
So I got around to attempting to replacing my O2 sensors. I could easily take off the rear one. However I noticed that the wiring for the stock O2 sensor was longer than the part I got from Underdog Racing Development. I probably will have to return this and go stock.
Did anyone run into this problem when replacing the rear O2 sensor? The part I got from Underdog Racing Development was: 234-4154. Which it says is the correct part for 1999 & 2000 49 State manual V6 2WD & 4WD; Rear: 234-4154.
Oxygen / AFR Sensors - Underdog Racing Development
Oh and by the way, I did confirm with the label under the hood that my car meets all 50 state emissions regulations.
Did anyone run into this problem when replacing the rear O2 sensor? The part I got from Underdog Racing Development was: 234-4154. Which it says is the correct part for 1999 & 2000 49 State manual V6 2WD & 4WD; Rear: 234-4154.
Oxygen / AFR Sensors - Underdog Racing Development
Oh and by the way, I did confirm with the label under the hood that my car meets all 50 state emissions regulations.
So which is it ?
Are all P0420 codes the same ?
Does an OBDII scanner say P0420 Bank 1 or P0420 bank II
If the scanner reads Code P0420 Bank 1 low whatever ??- can that still be the rear O2 sensor ?
I replaced my a/f sensor in front of Cat 1 with Denso 234-9002 @ 141k miles about 2-3 months ago.
Previous owner did rear O2 @ 95k - current miles are 143k
P.O. also did @ 130k - MAF,plugs,wires,fuel filter,timing belt,water pump
I will check for exhaust leaks tomorrow, I will get the multi-meter out and check the a/f sensor to see if that pooped already,but that code was a different one than P0420 - those were P1130 & P1135 when the a/f sensor went bad- could it be a ground issue with the O2 sensor ?
Man it is cold outside,but I want to fix this sucka
imp:
Nelsonmd
New member
I ran into the same problem when I did mine. Do you have a manual or an auto? The auto rear sensor is 234-4162 (4162 appears to have a longer tail). I bought 234-4154 on accident and had to splice on an extension. I think I may have done it wrong though, because I still have the P0420 code; or maybe I just have a bad CAT.
Why would the O2 sensors be different for manual vs automatic transmission?
BTW, IIRC, on non-cali models, the front O2 sensor won't affect your gas mileage.
So which is it ?
Are all P0420 codes the same ?
Does an OBDII scanner say P0420 Bank 1 or P0420 bank II
If the scanner reads Code P0420 Bank 1 low whatever ??- can that still be the rear O2 sensor ?
I replaced my a/f sensor in front of Cat 1 with Denso 234-9002 @ 141k miles about 2-3 months ago.
Previous owner did rear O2 @ 95k - current miles are 143k
P.O. also did @ 130k - MAF,plugs,wires,fuel filter,timing belt,water pump
I will check for exhaust leaks tomorrow, I will get the multi-meter out and check the a/f sensor to see if that pooped already,but that code was a different one than P0420 - those were P1130 & P1135 when the a/f sensor went bad- could it be a ground issue with the O2 sensor ?
Man it is cold outside,but I want to fix this sucka
oh yeah- 2000 Sr5 4x4 Auto V-6
thx..
TheDurk
Elite Member
My answers in bold.
