P0420

[Funkdog]

Went to Autozone got a p0240 code error, guy said it's either a bad o2 sensor or I just got some bad gas???

Could it really just be bad gas, should I just run this tank almost empty, then put some good stuff in with some Berrimans and see if it goes out?

Man, when lights lit up on my Super Beetle it meant trouble now!! Is it safe to run the car with the light on to see if it goes out on it's own? Sorry for the paranoia, like I said, with an old Beetle lights=bad things.

[o2xtype]

i would empty the tank first and see it alot cheaper that way and run some octane boost through it when you refill but thats just my opinion

[Funkdog]

Yeah I think I'll go get me a can of Berrimans and run it through there while this tank is still 3/4 full. Let it run down, probably in about 4 days.. and fill it up with Premium.

From reading previous posts apparently the V6 doesn't like anything but premium gas, didn't know that, so I'll start filling it up with that, and run some cleaner through and see if that clears it up.

Thanks.

[Funkdog]

BTW the full error is

Catalytic Efficiency below threshold (Bank 1).

So if anyone has any other ideas i'm all for hearing them.

thanks.

[Fishboy55]

That's usually a bad O2 sensor code. Bank one is the front bank exhaust manifold. If the O2 sensor is working properly the next time the system scans it, the light will go away on its own.

I wouldn't waste my money on injector or fuel system cleaners. They don't do anything more than the detergents that are already in your gas. Our resident Mitsu tech has stated this a number of times.

[Funkdog]

Forgive my ignorance, doesn't the system scan it everytime you start the car?

So if after the light comes on, and you shut the car off, then start it again and the light is still on, then it would be bad?

I've only had the car a week, and got it used, no problems up until now.

thanks

[Fishboy55]

I don't know the inner workings of the ECU either, but my understanding is that certain functions are scanned periodically and some are scanned constantly. I thought the O2/Emissions functions were one of the periodic ones, but I could be wrong.

[Funkdog]

Well I diconnected the battery to reset the computer, and the light went out as it should, so we'll see if it trips it again.

[manybrews]

its not going to be "bad gas", nor is using premium or anykind of fuel additive going to help.

if in fact your cat is dying, the only fix is to replace it.
however, a weak O2 sensor could toss that code by mistake. That is unlikely, though.

[Funkdog]

Manybrews,

If it's a bad cat then what kind of prices am I lookin at to fix it? I read that the 02 sensor is like $170.

thanks

[manybrews]

if its a bad cat, you just need to replace it.
I would think it would be around 400 bucks, but dont quote me on that.

[debull1999]

Your 02 sensor falls under your catalyst monitor in your pcm. It should clear itslef after 3 continuous good drive cycles if it is ok. Your MIL light will then go off. A drive cycle is just a weird pattern of driving involving accel, decel, constant high way speed accel and decel and idle...maybe not directly in that order but u get the picture. The code however will stay in your pcm for 40 continous warm-up cycles before it is totally cleared. And for a warmup you need to bring your coolant temp up 40 degrees f. and reach 150 f . So just turning your car on and off wont just do it. Pay attention to see if its a recurring code. Rich dtc's are a plenty and could set off your 02 sensor from an assortment of things down to a disconnected vacuum line on your fuel pressure reg. or a bad tank of gas....Hope that helps a bit.

[Fishboy55]

<div class='quotetop'>QUOTE(debull1999)</div><div class='quotemain'>Your 02 sensor falls under your catalyst monitor in your pcm. Â*It should clear itslef after 3 continuous good drive cycles if it is ok. Â*Your MIL light will then go off. Â*A drive cycle is just a weird pattern of driving involving accel, decel, constant high way speed accel and decel and idle...maybe not directly in that order but u get the picture. Â*The code however will stay in your pcm for 40 continous warm-up cycles before it is totally cleared. Â*And for a warmup you need to bring your coolant temp up 40 degrees f. Â*and reach 150 f . Â*So just turning your car on and off wont just do it. Â*Pay attention to see if its a recurring code. Rich dtc's are a plenty and could set off your 02 sensor from an assortment of things down to a disconnected vacuum line on your fuel pressure reg. Â*or a bad tank of gas....Hope that helps a bit.</div>
Wow man, welcome to the boards. Pretty impressive post for your first. Sounds like you know your way around the emissions system and ECU. You're gonna get swamped with questions.

[Funkdog]

Thanks for the help, almost to E on the tank and will fill it up with the highest octane gas I can find, see if that helps.

thanks

[Funkdog]

Filled the tank with 93, reset the computer, light went out of course... got about to 1/2 tank and it came back on... so I'm assuming I definately have a bad 02 sensor or my cat is failing, correct assumtion?

[Airbus A320]

My cat just went bad on my 2001 ES, but no lights ever came on, on my istrument panel. The dealer is gonna put a new one on next week. If it is your cat that is going bad it should be under waranty. Two Mitsu dealerships told me that our cats have an 8year/80,000 mile waranty on them. My stuff went bad after 75,000 miles so I just made before I would have to pay out the ass for a new one. Make sure you ask the dealer about the waranty. Good luck bro!