a4avant99

I normally use Shell gas. Since I am owning the car for just under a year, the engine lights (P0421) came on two times, both after using a tank of non-Shell gas. The light came on the second or third time starting the car after Shell gas is added following the tank of non-Shell gas. The light goes away itself a few days later. When I first got the light, I was told the catalytic converter is problematic, and I changed the spark plugs as the first step towards a fix. I think my catalytic converter may at a critical point. But no panic to spend the money for a new cat in a hurry.

2.7Lturbo

it could also be your sensros, everyone is so quick to damn the cats.

also i highly doubt it has anything to do with the gas you put in, that was just a lucky coincidence

GTA_Driver

On a 13 year old vehicle? It's the cat.

GTA_Driver

No need to spend the money on a new cat. Assuming your O2 sensor is fine, you can just install a spacer for it, it'll make the CEL go away and you can still pass emissions.

rohit13

X2

2.7Lturbo

so instead of testing the sensors, which there are several tests in the vag-com program you can perform, we jump to the cat being dead based on its age?

that is preposterous, age has nothing to do with the cat being bad, now if he gave us mileage then yes we can correlate age and mileage to come up with a life expectancy for the cat.

test the sensors, im not saying the cat is fine, but i am saying to test what you can easily test to narrow things down before jumping to conclusions.

GTA_Driver

Of course before replacing any part, one should be sure that it's broken. By all means run the tests.

There's nothing preposterous about my guess. A 13-yr old car has likely over 100K miles, and Audi warranties emissions equipment at 8 yrs/100K miles if I'm not mistaken.

My A6 cat failed at 130k, others had it come sooner.

Of course if it's just the sensor, then great, but I doubt it.

2.7Lturbo

your guess is based on normal usage, i will give you that.