ToyoRunner94

hey guys,

took my 2000 4runner in to get an inspection and they failed me because an OBDII reading came back. P0420 is a known code and i know it has to do with the catalytic converter but the bank reference is weird... the form they printed me says: P0420 Catalyst System Efficiency Below Threshold (Bank 14). i have never heard of (bank 14). i have always just heard Bank 1 or 2 to tell you which sensor is out...

any ideas?

Tom

mt_goat

That's a misprint, there is only bank 1 when it comes to cats on our trucks. Bank 2 emissions data is for vehicles with dual exhaust ie...4 cats, 4 O2 sensors. My BMW has 4 O2 sensors and I get obd II readout on bank 1 and 2.

ToyoRunner94

my inclination then is to just replace the o2 sensor first and if that doesn't work then look into a new cat... from my understanding though, Bank 1=sensor before cat; bank 2=sensor after cat... correct?

mt_goat

If you look up OBDII codes this is what it should say for code P0420:
You would get code P0430 for bank 2:

ToyoRunner94

have you replaced an o2 sensor before? i've been told it really won't matter if i use OE or advanced auto... any thoughts?

mt_goat

Wrong, bank 1 is one side of the V engines, bank 2 is the other side. Or in the case of an inline 6 engine with dual exhaust (like my BMW) bank 1 is one side of the dual and bank 2 is the other 3 cylinders.

mt_goat

Yes I have, and I've only used OEM sensors. Might check the prices here:

http://www.urdusa.com/product_info.p...s_id=430006000

ToyoRunner94

1999 & 2000 49 State manual V6 4WD; Front: 234-4161
1999 & 2000 49 State manual V6 2WD & 4WD; Rear: 234-4154

this was copied from URD... i think this is what i was referring to... see it says front and rear... so that doesn't apply to the position relative to the cat, its the position on the engine? so i would need the front?

mt_goat

The ECU is monitoring the emissions at the front O2 sensor and comparing that to the emissions at the rear O2 sensor and checking that the cat or cats in between is doing its job. So I guess it could be a faulty front sensor or a faulty rear sensor or a faulty cat or cats, or I guess an exhaust leak somewhere too could cause a P0420. I would think though that if it were a faulty O2 sensor (front or rear) you would get a code for that too, but I'm no expert.

ToyoRunner94

are these codes just a guessing game or if i take my truck say to advanced or toyota, could they get further info on exactly what the issue is? or is it just kind of guess and test and see what turns the CEL off?

mt_goat

Given the cost of cats, I'd probably start with the O2 sensors too. Or actually you could just install this P0420 eliminator box http://www.urdusa.com/product_info.p..._id=1230100014

Yeah even the dealers will sometimes just be guessing, check this out:
http://www.ttora.com/forum/showthread.php?t=93770

and this:
https://www.yotatech.com/forums/f2/t...verter-164833/

ToyoRunner94

thanks Dale, appreciate the info

Ohio4R

the sensor before the cat is called bank1 sensor1 and after the cat is bank1 sensor2

TheDurk

A good tech can do more than just pull the codes by looking at the sensor outputs and putting the car through a test run procedure. I can do it with a BR-3 hooked up to my laptop. Advance will probably not do this for you; they just pull codes. Some dealers may pull the P0420 and say "Change the cats, $1800". Others may do a better diagnostic.

If your sensors are at 70k+, it makes sense to change them and see if it helps. They will go soon anyway. Also check for exhaust leaks as that is the other cheap(er) fix. My 99 started throwing P0420 about 25k ago but I reset it and it goes 3 or 4 months. I can see from the sensor outputs that the cats are working, but the trip algorithm must be pretty sensitive. If the trips accelerate, I'll have to bite the bullet and swap the cats; I have done the sensors. For you, I'd see how long until the next P0420. You can do the "pull the battery cable" thing and pass inspection, unless your state requires a repair invoice. Mine does. NEVER go to inspection with a CEL lit up, you are just wasting your time. Good luck...

For the record mt_goat is spot on with the sensors--there is no bank 2 on a 3.4 L and sensor 1 is the A/F before cat sensor that feeds the ECU. Sensor 2 is the after O2 that is only used for throwing codes--that;s why the rear simulator works. The code is thrown based on a comparison of the two; so if there is no difference the cats aren't performing and you get a code. Dead sensors will throw other codes--merely degraded ones might not.

ToyoRunner94

I ended up buying a front o2 sensor from URD. I checked out the link Dale provided and i found a matching sensor for my truck so I figured i'd start with a cheaper fix and see if that is the problem. My truck has 122xxx on the odo and I have no indication that the sensors have ever been replaced. I had the code pulled twice at two different locations and both came back as Bank 1 and neither mentioned Bank 2 so i'm not going to worry about the rear for now. I should get it in a few days so we'll see what happens.

mt_goat

There still seems to be some confusion, "bank" is different than "sensor". Sensor 1 is before the cat, sensor 2 is after the cat. Bank refers to one half of the engine and in the case of a vehicle with dual exhaust, 1/2 of the exhaust. The 5VZFE doesn't have dual exhaust so there is no bank 2 after the crossover.

But anyway, I'd probably start with the front sensor too since its the most important to engine performance and the ECU's self-tuning adjustments. If that doesn't work then try replacing the rear.

TheDurk

I hope you got a front A/F sensor and not an o2 sensor--they are very different. A/F in front = Sensor 1 o2 in back = sensor 2. As mt_goat says, there is no Bank 2 on a 2000. Front first then rear is good advice--that's what I did. But at 122k+ I see both in your future if it is the case they have not been swapped. The P0420 will give no info on front vs rear as it is based on a comparison of the two, ECU doesn't know which is the problem. A look at the voltage curves can help here.

ToyoRunner94

1999 & 2000 49 State manual V6 2WD; Front: 234-4162
1999 & 2000 49 State manual V6 4WD; Front: 234-4161
1999 & 2000 49 State manual V6 2WD & 4WD; Rear: 234-4154

these are the listings on the URD site where i bought the o2 sensor. i was under the impression the o2 sensor is what throws the emissions code p0420 catalyst below threshold (bank 1)... did i get the wrong thing? i'm confused what i should actually be getting now...

TheDurk

Are you sure you are 49 state? If you are, then I am wrong and I apologize--front and rear are o2. I thought 99 was the last year for 49 state and Cali being different. In any case, make sure because Cali trucks were sold all over the place, I bought my '99 in NJ and it's Cali. Cali has A/F in front and two cats, 49 has o2 front & rear and only one cat.

ToyoRunner94

Now that you say that, i'm not sure if i'm 49 state. i actually had it shipped in from a carmax in las vegas. is there a way i can tell where it was made?