I have a 2001 TRD Tacoma 3.4 automatic. This stupid code popped up a while ago and it said insufficiant catalyst bank one. I changed both converters and a little while later it came back so I changed the front O2 sensor. It still came back so I changed the rear sensor. It came back again so I changed all of the exhaust gasket but guess what? It's back!! Does anybody have any idea what could be going on?

 

I got one of these, problem solved: http://www.urdusa.com/product_info.p..._id=1230100014

 

I noticed the previous owner had my O2 sensor changed from past records. Every time I go wheeling it throws the code, so maybe it's just loose, I'm not sure. I just clear it with my scan guage and it goes away until the next time it gets bumpy.

 

Yeah check the wiring going to the rear O2 sensor, maybe the connector is loose or the wiring got melted by the exhaust...etc...

 

Wow! thats over $1500 worth of parts there....I can tell you that the code will happen when the computer see's the front O2/A/F sensor match the rear sensor...This could happen if there is an exaust leak upstream from the sub 2..Or Your cat is not working...Did you use new toyota cats? or used or aftermarket,Just because I do not believe the aftermarket cats hold up very well.....I know Toyota "used to" warranty fed emmision componants for 5yrs,60k...weather it was on a new vehical or installed in the dealer......I know cause we had a bad rash of sulfer cotaminated gas in the stations here and we replaced a ton of them..several times......

That URD Rear Oxygen Sensor Simulator looks to be the way to go...it sure does beat pulling the CEL bulb from the cluster...

 

Yea I used aftermarket cats but they are only 3 months old. I also used aftermarket sensors and suspect they could be the problem. I just hate throwing more parts at it. The truck only has 95,000 miles on it so I really doubt it was the converter in the first place but I did spend 7-8 hours idling every Saturday night at the race track using my truck as a rescue vehicle. So I thought maybe I had burned them out. I hate to just remove the bulb just in case something else goes wrong and I dont get a light.

I too thought it was an exhaust leak that's why I replaced all the gaskets. I guess I could just keep clearing the code and live with it. I've actually left it right now thinking that maybe another one would in come pointing at something else if I gave it a little more time.

I also tried different gas since I had been running midgrade from Speedway since it's the same price as regular. But running regular from BP didn't change a thing.

I may try the URD part. Thanks for the tip!

 

aftermarket cats = fail

aftermarket o2 and a/f sensor = fail


I bet you could have just changed the front [o2/or/a/f] and rear 02
and your cats were fine.

anywho that is in the past.


anyway when it comes to emissions codes [or anything that triggers a MIL] stick with toyota oem parts from toyota dealers
and you will get the best results, save the most money in the long term, and remain legal

 

All 2001 3.4 Tacos use a A/F sensor in front.

 

Thanks guys! I'll let ya know what happens next.

 

great info in the archives!

i've been having the same problem w/code 420. in the last 6 months i've changed both sensors- engine light keeps popping back on no matter what, and some times, after the c.e.l. has stayed on for a couple hundred miles, the truck actually gets worse mileage, and bucks a little pulling the steep hill to my driveway (3rd gear 30mph) when the light's off, the truck runs great & most of the time with the cel light on, it runs great.
tried using shell 93 exclusively-still comes on. getttin tired of resetting it.
i don't off-road her-ever. just my daily. next step would be to replace the grand or more worth of converter/downpipe or try the URD simulator .

what would y'all do? THANKS!

 

URD sim

 

even using the bone stock exhaust?

thanks!!

 

Sure, why not?

 

sounds like a plan then! taking my taco from tn to utah at the end of the month hauling two bikes (1wdftw!-lol) and two weeks of camp gear- waiting on my URD simulator-hopefully i can enjoy no cel and better mileage!
testy little emmisions systems they have, huh?

thanks again!

 

Yeah, especially the 2001 and up (front A/F sensor).

 

thank again for the input- ordered but not here yet.. can't wait!

gonna be a 1700 mile trip (one way-argh!) to utah from here in nashville- know the altitude change will effect her power. ..it's all uphill getting there!
i'm praying this little deal helps with the power loss, mileage.. and the codes. i hate seeing that dang light on!!!

 

URD sim does nothing for performance/economy as the rear sensor has no effect on them either. All the rear sensor does is set codes.

 

i didn't think putting it on would help performance or mileage- thought keeping the codes off would, and that's what it claims to do- trick the system=no code/c.e.l.
but i'm really not sure at all, i swear!
Does the computer compensates when there's a codes- somehow by running different when it's throwing the 420? i might have just been paranoid, but i really think she hesitates and gets worse mileage with the code/cel on.
try to keep it cleared for the most part..

thanks for your input.
more!!

 

I don't think P0420 alone can affect the running of the engine. Some of the other sensor codes do keep the ECU from running in closed loop. That is, the ECU decides it can't trust the feedback it is getting from the front A/F or O2 sensor and it stays in open loop (start-up mode). THIS will for sure cause things like hesitation and poor mileage. I will accept a ruling from a higher authority on this; I am not an expert. Your obdII scanner that reads your codes should be able to tell you if you are running in closed or open loop, mine does.

 

i see... (kinda) . i'm not a mechanic at all.. most of the normal repairs i understand. i hate this pooter stuff!!

i guess i'll just have to wait and see. the part should be here tommorrow or tuesday. i'll sure let y'all know how long the light stays out after i intall it. hope and pray it stays out for good!

thanks for explaing that to me. i just learned something! (open loop) need to get myself a scanner. been borrowing a buddies once a week or so..
one more question... does anyone use one of the cheapy code scanners on a regular basis (the under100 buck ones-see 'em in harbor freight and @ the zone) worth a fart?