oldracer

Well over the weekend I was still looking at what to do about my possible failing catalytic converter. I saw on here some people used GM Parts Direct: Your direct source for Genuine GM Parts but said the shipping costs were so bad that prices evened out to a dealer. Well, those folks are pretty much right as I emailed my car info (including vin) to those guys and the total cost was $15 less than the dealer and probably higher once I figure the core return shipping cost into things. So a dealer/internet cat is about $820 give or take a little and I am still checking on the CARB approved generic cats such as Magnaflow, etc.

skyline26

try out RockAuto as well...better prices and shipping is decent too

donbrew

I installed my new catt Saturday. P0420 came back. Has anybody been in your computer with a Tech2 scanner? I am now thinking a clueless GM tech screwed mine up.

oldracer

Here is a bit more information. I talked to the owner of Black Forest Porsche - BMW Repair in San Diego and he said a cat, even one labeled as "generic" that has the right numbers from the Air Resources Board is fine to use. They do that on a lot of the older models of Porsches since a factory replacement cat can cost more than the car is worth! He asked how old the O2 sensors are and I said 127K miles and he said that they should be replaced so I have ordered the one after the cat and will replace it next week when RockAuto.com gets it to me. He noted O2 sensors usually last 60K to 70K when burning the terrible gas we have no with all the chemicals that are added to it as most of them do not burn and can even act like leaded gas at times!

skyline26

hey donbrew...what cat did you use?
A "high flow" cat will trigger the p0420 or possible an aftermarket could cause this too.
If the air flow rating is off, these cars wont like it. Very finicky

orrr you can get a tune and not worry about it also hhaha

donbrew

No "performance" parts here.

donbrew

Update: I installed 4 new injectors; passed the catalyst test and cleared the P0420. With the "Canadian cat", now I have a complete cat with O2 sensors cluttering the garage.

oldracer

Good update time for me too. I had done the injectors earlier in the year and when I was flapping around about this earlier I mentioned I had replaced the O2 sensor #2 and that seems to have cured the issue with the engine light and all the tests have completed fine. My Porsche mechanic friend is right it seems, replace the O2 sensors about 60K miles even if there are instructions to do it.

donbrew

For me I did things in the order "they" say to do it, the expensive way!
1. #2 sensor
2. #1 sensor
3. new cat
4. new exhaust gaskets (with the cat)
5. new injectors

The reason I went with new injectors is that I got them for $22 each. Testing/cleaning them would have cost $20 each + down time.

Forgot. I also tried a new ECM after the new cat.

donbrew

Dammit, I knew I shouldn't mention it. It came back, but only as a pending code not a permanent code.