Is my local stealer ship trying to F$% me?

[hitbychance]

Hey guys,
first off this could go in technical forum but i need a quick response, here it goes,

Recently the engine light came back on in my 08 350z, i bought a reader and check it and got the code
P0420 Catylist Efficiency Below Threshold Bank 1
From what i read on the net this is caused by O2 sensors or catalytic converters. Knowing this i took my car to nissan as the emissions is still under warranty, they just called me up and said i need a MAF (mass airflow sensor) and it will be $445 plus taxes for the part and one and a half hours labour, they also said i should not drive it with it needing a MAF. What do you guys think? I personally think they are wasting their time ordering a sensor that may not fix the problem and i will not pay for.

[BusyBadger]

While it's possible that it's a MAF you can place me firmly in the "I doubt it" category. Out of the 5 firsthand instances (guess that will happen when you keep a code checker in your car!) I've had with either a Bank 1 or Bank 2 inefficiency CELs, one of which was my own, it's been the catalytic converter in every instance.

I rolled into my dealership and let them know what was going on and they ran a catalyst efficiency test on it that cost $50 or so, but was fully refundable if it did end up being the cat (which it was - and the other one went while it was in their shop). I'm wondering if your place even offered that to you. There's a Federally mandated 8yr/80K mile warranty on catalytic converters, your dealer could be telling you something hoping that you'll go away so they don't do work they aren't getting paid for - which is complete crap but we all know it happens. Is there another dealer that you could take it to to get a second opinion? It might even be worth asking about the catalyst efficiency test up front.

[hitbychance]

Thank you Badger!, i went to pick up my car and i brought my code reader, payed the charge to read it and then i jumped in my car before i left i tested it again, no codes, they said they cleared the codes, but shouldn't the light come back on or atleast trigger a code if nothing was repaired? They said the sensor will be in tomorrow but i'm thinking of not getting it until atleast the light come back on. We don't offer those cat tests as there is no emissions laws here.

[BusyBadger]

I forgot that you're down in Oz, land of all things toxic and sinister!

I'm surprised that they still don't offer the catalytic efficiency test though, it seems like it would be the only way to determine if it were the sensor or the cat(s). The code should pop up again, mine got to the point where it would go every 15 or 20 minutes after I cleared it before I took it in. I suppose if it is a cat instead of the sensor you could just go with a high flow cat instead of the oem version. Even if you weren't looking for the couple fo extra hp you'd be getting from an aftermarket HFC you'd still be saving a good amount over an oem one.

[hitbychance]

So my light came back on after 100 miles, after speaking with a few mechanics they all said basically that its my cat or o2 sensor and that its ok to drive, also to not go back to that dealer at all lol. currently saving for some HFC's

[BusyBadger]

A lot of HFC's will trip a CEL too. There are a few things you can do to keep this from happening, the one I've seen most people use (and love) are from TiTek. Remember to order a pair of them if you go this route.

[hitbychance]

i was looking for these too, thanks for the link!

edit: recommend any brand of HFC?