Number of catalytic converters Saturn Astra

Could someone tell me how many catalytic converters a 2008 Saturn Astra has. Specifically I am trying to find out if the second cylindrical object in part 14 is a secondary catalytic converter. See the link for the parts diagram. Any help with the matter would be greatly appreciated.

That’s not a catalytic converter. It’s a resonator/muffler.

Catalytic converters have O2 sensors downstream of them. As you can see in the image.


Thanks for the reply.

So I was told it was a converter by a muffler shop and I asked them why does it not have an O2 sensor, they said that the second one was not monitored. Could this be true?

Also, what is the purpose of a resonator? and why would this car have 3 resonators/mufflers?

Don’t go back to that muffler shop.


well his point was to take it to the dealer and have it fixed under warranty. He said that he had the same car come in a week or so prior. That guy did not want to deal with the dealer and just had them fix it. He said that when they removed that pipe that cylinder had a “biscuit” meaning it had to be a converter.

If there’s a problem with the catalytic converter, it’s covered under the manufacturers warranty for 8 years/80,000 miles.

So why are you dealing with a muffler shop?


had a “biscuit” meaning it had to be a converter

Don’t go back there

They don’t know what they’re talking about

The converter is not bad, the flex connection failed. According to the warranty any piping between catalytic converters is covered. Thus, if this is a secondary converter it should be covered, if it is not then it should not be covered.

From what I read secondary converters are common in European cars to deal with cold start emissions reductions, which are part of their standards.

Why would this car have 3 resonators/mufflers?


#14 is NOT a converter

The converter and its piping are fine

Go to another exhaust shop that actually knows their stuff

Or go to a Chevy dealer and have them replace that part

how can one know if it is a converter or not? the dealer could not tell me what it was just that they would not cover it under warranty

The section between the gasket (#13) and the oxygen sensor (#21) looks like it might be a secondary catalyst.

Look at the image again.

Item 18 is the pre-cat. Item 20 is the pre-cat O2 sensor, Item 21 is the secondary cat O2 sensor.

Everything after that is just exhaust components.


The first cylinder just before item 21 is the flex connection, which is the part that is failed. I still do not understand how one determines if a part is a CAT or resonator.

Must be a flex joint then. The second half of #14 looks like a resonator, they are generally needed in that location to eliminate a drone type noise. You could cut the old pipe off and look inside or check the service manual for identification.

Find a muffler shop who has the abilty to weld something like this in.

They’re as common as snot.


You have two warm up cats that are attached to or part of the exhaust manifolds, there should be an O2 sensor just in front of those. Then there is the three way cat at the beginning of the exhaust pipe with an O2 sensor just behind the cat. All three O2 sensors are monitored.

That little bulge in item 14 is called a resonator but it may be nothing more than an expansion chamber that absorbs the shock wave (aka standing wave) that can develop in an exhaust system. The standing wave is good in a race car where it can be designed to correspond to the peak RPM of the engine to scavenge out the exhaust gasses, giving more power to the engine, but not good in a street car where it could damage the cats.