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Discussion Starter #1
About 4 months ago I replaced my Catalytic converter in my 2005 Colorado with a Flowmaster Catalytic converter, After the replacement my check engine light came on. I took my truck to the dealership to check the light and according to them my new converter does not create enough back pressure and that i need to replace it with a GM replacement part or the code will not go away. Does that make any sense?
 

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Nope.

Here's a more likely explanation:

Your new catalytic converter is not burning off the excess oxygen as well as the stock one did. The rear O2 sensor is picking up on that and throwing a code.

The quick fix is to get an O2 sensor spacer and install it under the rear O2 sensor. That will space the sensor out of the exhaust stream and bring readings back to normal.

If you knew the exact trouble code it was throwing that would be helpful too.
 

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Discussion Starter #3
The rear and front o2 sensors are both GM replacement parts, and both have less then 25 miles on them. According to the dealership the code has something to do with the converter not the sensors
 

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The rear O2 sensor "senses" how well the catalytic converter is working. That's the only reason it is there.

So if your new cat isn't working quite like your old one, the rear sensor will be the one to let you know (with a code).

You can trick it into thinking the cat is ok with a spacer.

Hope that makes sense.
 

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Complete nonsense.
Totally. The whole "engines need backpressure" argument is ridiculously flawed. It's based on a complete mix-up of cause and effect.
 

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Well there, easy fix!

............moving on
 
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