190hpKiLLA

iTrader: (11)

Anyway, my lovely check engine went on. Just like with women. Cant live with them, cant live with out them.

I was cruising @ 80-100MPH for a good 100miles. then BOOOOM,(not the engine) The light came on. I checked the code and its>>>>>>>

**P0420** Catalist efficiency Below threshold(bank one) haynes manual says its catalyst sysem fault. Go firure

So what can it be?

Thank you.

MoCoMax

I got the same code at the same time my coil codes were thrown. I'm not sure what fixed it, but I do know the ECU was reprogrammed for the throttle cut-off TSB and one coil was replaced. Haven't thrown the code since.

I also found the following:
Service Bulletin Number: NTB99019
Bulletin Sequence Number: 480
Date of Bulletin: 9904
NHTSA Item Number: SB604788
Make: NISSAN
Model: MAXIMA
Year: 1998
Component: EXHAUST SYSTEM
Summary: SERVICE MANUAL PROCEDURE CHANGE FOR REAR OXYGEN SENSOR DTC(S) P0137, P0138, P0139, P0140, P0141 AND THREE-WAY CATALYST DTC P0420. *TT

Hope this helps.

John

190hpKiLLA

iTrader: (11)

Thanks but i still dont know WTF is wrong cause I replaced the coils(6 of them) 2days ago and resetted the ECU by disconnecting the battery.

MoCoMax

If I had to guess, I'd say it was a bad O2 sensor.

190hpKiLLA

iTrader: (11)

Whats this FUEL cut off thing you were talking about???

Larrio

iTrader: (10)

the code it's not performance oriented

most members including myself on the west coast forum get it between 20-40k miles.

I just took it in to the dealer. They downloaded a new ECU program, cleared the code, and i'm clean free. No charge diagnosis, nada.

190hpKiLLA

iTrader: (11)

I mean the car has great gas mileage. i have 95K miles (dont ask) Do you think the dealer will download the new software for me????

Why is the software for?? I have a 2K maxima 5spd

SR20DEN

iTrader: (7)

Theres that dang code 420 again. Your Maxima has had too much Chronic.

190hpKiLLA

iTrader: (11)

ye we both we smokin that Goos ShiiT but I guess she couldnt handle it. The previous owner never let her loose like that before.

MoCoMax

The throttle cut re-program helps reduce the on/off thrittle sensitivity that the manuals tend to have when under 1800 rpm in 1st gear. It's something that the dealers are supposed to do routinely when the car is in for service.

The TSB can be found in the stickies.

Larrio

iTrader: (10)

isn't that for the electronic throttle on the 2k2-2k3's???

190hpkilla: i'm pretty sure they'll do it for you. Just make sure they won't charge you for a diagnostic before you pull in by calling in advance.

190hpKiLLA

iTrader: (11)

Thats what I want to know, so before I start the fight I want to make sure the thing is for my car.

HitManSE

iTrader: (1)

Ok the P0420 code is for cat converter efficiency bank 1. Well what that means is ur pre-cat(the one by the radiator) sucks. U can either get used to the SES light like I have . Or get a new pre-cat which comes with the complete factory y-pipe $500 approx. So the choice is urs, id just get a y-pipe (if u dont already have 1 that is) and dont worry about it. Ur car isnt sick, it just wants less cats.

MoCoMax

The TSB I'm referring to is for the 2k-2k1'S. Here ya go.

http://www.nhtsa.dot.gov/TSBScans/sb625926.pdf

190hpKiLLA

iTrader: (11)

So if i get an aftermarket Y would the check engine go away??
Does keeping the busted pre cat reduce performance??

Does anyone know the symptoms of the "Engine - ON/OFF Throttle Sensitivity At Low Speeds"

If there is a TSB out does the dealer fix it for free or I have to pay 4 it anyway???

Thanks.

MoCoMax

I'm not so sure, Hitman. I got the same code when I had coil problems, and I know the pre-cats were not touched as part of the repair. My codes were cleared and I've not gotten another one since.

Isn't it possible that the sensor for the pre-cat is showing a bad reading simply because of the improper combustion caused by a bad coil?

HitManSE

iTrader: (1)

The y-pipe will not make it go away. All that code means is that the pre-cat in bank 1 (by the radiator) isnt opperating efficiently. It doesnt mean its clogged just not reducing emissions enough, there 4 a y-pipe might just set it cuz, well they remove the pre-cat so how can it work efficiently? It doesnt mean busted, just not helpin reduce emissions enough u see there is an upsteam 02 sensor be4 the pre-cat to see what the emissions output is be4 it enters the cat and 1 downsteam which is after the pre-cat and if not enough emissions was removed by the pre-cat the SES goes on. I dont know the answer to the other two questions.

mingo

iTrader: (4)

yeop.. me too

HitManSE

iTrader: (1)

Well if the P0420 code is just an error in the ECU, than I cant confirm that. If the code P0420 went on while u were having ur coil problems then it just had to be a coincidence from my understanding. But the code P0420 is definetley low cat converter effiency in bank 1. I got it after I gutted my pre-cat (I have a Cali-spec)to get a complete y-pipe, then just half. But u do kinda have a point about the improper combustion, but if that happened all the fuel didnt burn in the cylinder so u should have also gotten a code sayin its runnin rich which would be picked up by the upstream o2 which is be4 the pre-cat so I dont thing it would set the P0420 code, but id ECU error is at fault then u never know but from my understanding it shouldnt set P0420.

MaxedOut2g

yea ive had P0420 for monthsnow...im pretty sure theres nothing else wrong cuz havent noticed any performance or gas mileage differences....only thing i know is that my emissions smell baaaaaad when i start the car.....im HOPING that its cuz i have a dirty k&n filter....it will hopefully go away once i finally get my apexi filter...
holla

Larrio

iTrader: (10)

your throttle is a cable and is controlled by your foot pressure on the gas pedal. Throttle sensivity ECU wise has to do with electronic throttles on the 2k2-2k3 maximas.

an aftermarket y pipe has nothing to do with your catalytic (correct way to spell it) sensor. The cat is not broken nor leading, the sensor is not broken nor needs to be replaced.

bottom line: just take it to the dealer for the new ECU fix or just clear the light yourself and be prepared for it to come back.

HitManSE

iTrader: (1)

So this whole P0420 thing is just an ECU error? Im not tryin to sound like a smarta$$ or nothin not do I have anything against u Larry so dont get me wrong, but when I gutted out my front pre-cat the ses went on and threw the P0420 code. At the time my car had approx 12K miles on it. As of this moment it has 25.1K and the damn SES has been on the whole time, I dont even bother resetting it cuz like u said it goes on again in like 5-10min. But is this just a coincidence with my car? Or is this really a major ECU error and the dealer will take care of it, even though I have a Y-pipe?

Larrio

iTrader: (10)

nah.. nothing taken in a bad way.

I'm sure it is a ECU because three so cal members threw the light right after installing our intakes. Irvine78 at low 20k miles with his stillen hybrid, mine at 21k miles with my injen, and foodmanry at high 20k miles. All of us have had our ECUs reprogrammed with the updated software after attempts to reset the light with no results. If the dealer gives you problems, i'll fax you my service write up and you can tape it to their forehead

MoCoMax

Sorry, Larry...you're incorrect. The on/off throttle sensitivity TSB is only for 2000-2001 cars with manual transmissions. It has nothing to do with the throttle-by-wire cars.

I attached the TSB earlier in this thread if you don't care to take my word for it.


John

PCGuRu2K

iTrader: (34)

Damn.. You just bought the car like two weeks ago and already you broke it

Larrio

iTrader: (10)

whoops, sorry.

MoCoMax

Noooo problem

190hpKiLLA

iTrader: (11)

So the bottom line is to:

1- Get The on/off throttle sensitivity fixed

2-Update the software for the ECU.

3-Just drive it like Ya stole it and hope the problem will go away.