so I had the codes for the O2 sensors/muffler (P0420: Catalyst System Efficiency Below Threshold) come up a few times. Since I have no money to go check the car, I just kept erasing the check engine, waiting for it to come back on.

Any ways I get in the car and go eat dinner, come back out in an hour, and now it's snowing and getting much colder. When I started my car for the second time, it took forever (cranking) to start.

Could a bad muffler or O2 sensor cause this to happen. Also if the muffler is bad, what exactly would it sound like.


this is a 2000 A6 by the way

 

no answers????

 

I cant remember well but i changed both of my O2 censors too like 1 year ago

i didnt intall them right the first time and the car wouldnt even turn on
it should be like 100 bucks for a good 02 censor beleive me ull need it, after u intall the new ones the car feels alot better

 

i changed alot on my car when i did the 02 censors so im not sure

hopefully a tech could respond

 

Similar situation I responded to in another thread..
What code are you getting? # / description? Is it Bank 1/2 Sensor 1/2?
I've had this code come up when a voltage drop occurs in the battery and the battery is on its way out. A poor battery may send random CEL's. Strange that it would send the same one over and over, but nevertheless.
Then you mentioned in cold weather, it was hard to turn over your car... again, very much a bad battery symptom.
I would get your battery checked and/or replaced (how old is it?) and see if that doesn't solve your problem. Turning the car over shouldn't be related at all to an O2 sensor.

ps. (sorry, I see you added the code, duh.) ok, not the same code I was referring to, but same troubleshooting applies.

 

I was thinking of the same thing too, that it might be the battery, I guess I'll go test it at auto zone sometime. As for the code, it says that its Catalyst System Efficiency Below Threshold (Bank 1). So it's Bank 1, not sure if that makes a difference though!

 

P0420 is for the main catalytic converter on the passenger side. What year is your car and how many miles are on it?

 

its a 2000 A6 with around 120000 miles

 

Federal emissions warranty cover catalytic converters for 8 years 90k miles... So you are out of luck on that.

Going back to the issue, I noticed in your other thread that you are hearing noises from the driver side? Your code is refering to the passenger side. Try to listen for the noise. I would bang on the converter itself and see if it rattles. If it does, then you need new converter.

Anyways, if your catalytic converter is really plugged, it can create hard starting issue. If you know of someone with VAGcom, they can test the O2 sensors to see if they are okay. Otherwise you may have to replace the converter.

BTW, considering the code is refering to your main converter, not the pre-converter, it is easier to weld on an universal converter instead of the Audi one. You will save a pretty penny doing that.

 

I have the unregistered ebay vagcom, would that test it?
also is it okay to drive the car for a while before fixing it?