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2003 Passat Catalytic Converter Error Code

My Check Engine Light came on and my mechanic tells me the error code is a faulty catalytic converter. A freind of mibe had the same car. He sprnt a lot of maney changing the converters his Check engine Light still came on. Catalytics coverters raely go bad. Any other ideas?

Yeah, have the actual signals from the oxygen sensors looked at on a scope.

That code actually only says that the downstream sensor is not detecting a sufficient change in the oxygen level from the upstream sensor. It’s best to check the actual signals.

By the way, converters don’t “go bad”. What actually normally happens is that the catalyst, a platinum-palladium coating on a honeycomb substrate, gets contaminated. Only if the exhaust molecules can actually come in contact with the “sweet metal” (I made that up…you guys like it?) can the catalyst cause the oxygen to become free from the nitrogen again to change carbon monoxide into carbon dioxide and hydrocarbons into spent fuel (CO2 and H2O ideally).

Typically this contamination is from burning oil, which can also contaminate oxygen sensor. Burning any oil?

The catalytic converter in your vehicle is warranted for 8 years/80,000 miles by the car manufacterer. If you fall under these limits, the dealer has to install a new cataltyic converter at no cost to you.


I have 91000

I don’t “burn” any oil. However, since the car was new, I have had to top it off with a quart or two between oil changes. I use synthtic oil that VW recommends and change it close to the recommended 5000 mile interval. If I use regular oil, morw frequent oil top-offs are required.

Whart kind of “Scope” My mechanic showed my the hand held device that plugs in under the dashed. It was showing all kinds of readings.