I have an 05 tc with CAI and about 54,000 miles and a CEL came on. Took it to a "Toyota / Lexus specialist" and they ran a diagnostic:

The Code read: P0420

- Gas leakage in exhaust system
- Heated Oxygen sensor (Bank 1 sensor 1, 2)
- Three-way catalytic converter

Technician said its most likely the 02 sensor.

Heres what I think MIGHT be the problem.
I have a CAI. I have removed the little black "grille" directly in front of it on the front bumper (where the aftermarket fogs fit). Furthermore: my plastic wheel-well cover thingy flew off on the freeway. So the filter to the intake is open to lots of dirt and debris. Do you think its possible that the MAF sensor is causing the CEL?

I wanted to buy an 02 sensor but i dont know which one to buy. I believe theres 2 (correct me if i'm wrong)

Also: I've read a couple threads about an "antiflour fix" but i'm not sure if it will work for me.

any HELP is greatly appreciated!!

 

Its hard to say what the problem might be. I dont think its from dirt being sucked into your intake, that would lock up your engine, not bring up an o2 code. Umm the spark plug antiflou fix it only good if you have an after market header. It just makes your computer read less air at the second o2 sensor. You didnt try running leaded gas or a fuel additive did you?

 

What do you mean by leaded gas? 89 or 91 octane? Because i always put 87 octane.

And no i havent tried any fuel addiditves? you think that might help? and how so?

thnks for the reply

 

Change the o2 sensor -- the one on the header -- I bet that will fix it

 

I'm assuming that would be the oxygen sensor on the "Front Pipe"?

Heres a link to both oxygen sensors on TRD sparks...

http://www.trademotion.com/partlocat...ke=37&model=Tc
(Enter 'Oxygen Sensor' in the search field at the bottom left)

Which one do i need?

 

if your still under warranty take it in, if you arent, take it to an exhaust shop so that they can take a look at your first cat. You can have it tested for like $50 (which is far less than the OEM A/F sensor, which was $200+) and if your cat is bad, it carries a federal warranty for like 10 years i think, and toyota has to cover it if thats the case.

 

Maybe i will.. but isn't it a little early for my cat to go bad? What should i do if its NOT the cat?? I have a feeling its either the 02 or the MAF... again... correct me if i'm wrong.

 

If your only running 87, you dont have to worry about leaded gas lol. they dont sell leaded gas at regular gas stations anymore. You have to buy lead additives to put into your gas tank. Lead plugs your Cat though. Most cars with a turbo(without a cat) or just a race header run leaded fuel because though dont worry about the Car. Lead raisign your octane level is all. But it you never used anykind of fuel additive thats not the problem..You can always just check to see if the o2 sensor is loss. That will turn on a CEL instantly. I know mine on the header rattled loss the one day.

 

Anyone else? I'm still not sure which oxygen sensor needs to be replaced

 

P0420 = catalytic converter efficiency low. If the Repair Manual in the Tech section was working I could link you directly to the description of this fault code. (Mods - hint, hint, ...) This is the cat in the exhaust manifold.

Take your car to a Scion dealer for a warranty replacement of your exhaust manifold, which won't cost you anything.

Btw don't mention your mods and don't let them try to tell you your CAI or exhaust caused the cat to fail because that just isn't possible.

 

My only problem with taking it to the dealer is that they charge $90 to do a diagnostic. And if they figure that the cause of the CEL comming on is not covered under waranty (for example the oxygen sensor) then my $90 goes to waste.

So i just want to be SURE that its the Cat Converter before i take it in to the dealer.

Does anyone else think its the cat converter?


ps. Ever since my CEL has come on i have been getting better gas mileage (about 20 mi. more per tank!)

 

Just called Norwalk Scion... Spoke with someone from the service department and gave him the code (P0420). He said he's convinced its the cat converter.

I'm taking it in today... i hope he's right

 

Good luck dealing with hustlers. My experience with dealers in the past is horrible. They blamed my transmission problems, on my injen cai, lol.

Thats all I have to say about that. Good luck though, you'll need it.

 

OK I just realized with 54,000 miles you are out of your basic warranty unless you bought an extended warranty. I would not take it to Scion just yet, they will charge you ridiculous rates such as your $90 diagnostic check which you can have done at Autozone for free.

Actually, if your car is otherwise running fine and your only symptom is the CEL, don't even take it to an independent mechanic just yet. Take it to Autozone or any other auto parts store that reads CEL codes for free and have them clear the code (that is unless your tech already cleared it.) It could just be a spurious glitch in the ECU. See if the CEL comes back, and then you can be sure there is a problem.

If so, have Autozone read it. If it's a P0420 again, first don't worry - this is not a serious problem, as you've noticed your car is running as well now as it was before the CEL. It's an emissions system problem that's all. Just post back up and we can take you through some other checks. There are procedures for checking the O2 sensors, and you can also check for an exhaust leak yourself. If these things check out then you have eliminated the possibilities down to the exhaust manifold.

If it does turn out to be a sensor or the manifold then that is the time to take it back to Scion and have it repaired (for free) under the warranty for emissions control as mentioned above by equinox2355.

 

We have some knowledgeable people on this site =)

Great to know that there are people nice enough to give free good advice.

 

Thank you, and i appreciate your help.

However... (Before I read your post) I took a risk and went down to Norwalk scion today.

I was very happy to hear that the problem was in fact the catalytic converter and it will be replaced under warranty with no charge to me!!

I’m freakin’ lucky because otherwise this problem would probably set me back about $300

The replacement part has been ordered and will be ready for installation in a matter of days. Now I have to convince them that my transmission problems are not caused by my CAI or my TRD springs!



Thanks everyone for your replies, and thank you Norwalk Scion for taking care of the problem.

 

catalytic converter

 

i just got mine replaced 2 weeks ago i had the same code , and you dont have to worry about warranty because its an emmisions problem, that part has its own warranty

 

Wow thats good news. Coincidentally My friend just started having the same problem last night. I'll let him know its covered under warranty.

 

Yes, sounds like your dealer is taking good care of you. Did they still charge you the $90 diagnostic or will that be covered also?