marmar1305

Hi. I have a P0421 on my 2008 Cayenne S. I compared the Volt values of the upstream and downstream O2 sensors between bank 1 and 2. They have similar values. I also compared the short and long term fuel trim values and they have also comparable values. The only difference I found was that the inlet temp of the cat converter of bank 1 is approx 85F lower than bank 2. I assume there could be a vacuum leak between the exhaust manifold and cat converter of bank 1. I will perform a smoke test to see if I can find a leak. Any advise would be greatly appreciated. Thanks

marmar1305

I did the smoke test on the exhaust system and engine inlet, it showed no vacuum leak anywhere.
Any suggestions more than welcome.

red996

I would probably visually inspect the o2 sensor wires for any brakes or frays. If nothing is damaged there I am not sure how I would proceed. I suppose you could try switching around the o2 sensors from one side to another to see if the code follows? That's assuming there are 2 upstream and 2 downstream o2 sensors? Not sure throwing parts at this is the way to go. So you replace the o2 sensors and you still get the code? You replace the Cat and you still get the code? That would suck! What's the mileage?

reacp911

Have you tried running thru some injector cleaner?

Also


Scotty is a bit eccentric but I think he knows his stuff.

theiceman

as this is more a regional forum than a technical one i would pose the question on the Cayenne forum, chances are someone has run into this before. That Kilmer guy is a total hack and if it isn't as Toyota he hates it. He actually goes out of his way to show German cars are way worse than they are.
Complained about Audi because the battery was in the trunk of an electrically operated trunk lid. he had no clue there are power and charging posts under the hood.. he is just loud and clueless.

reacp911

Unfortunately, compared to Toyotas, Porsches and German cars are relatively unreliable. It's one of these do you want to burn brightly, or for a long time issues. You are certainly right tho, whenever you have an automotive issue, the first thing you do is an exhaustive internet search.

Having your battery on the other side of a power only lid is a pita. Give me a cable any day