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2003 Eclipse Spyder GS 2.4l 181k miles bone stock. Got a P0421 code over the weekend. Car runs really good other than throwing this code. Whats the best way to fix this?
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Every thing I read tells me you have a bad cat. But there is a fix for that beside having to replace the cat... Just type into your Google browser and lots of stuff comes up
Type this How to fix a P0421 code ... Hope this helps you...
 

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Every thing I read tells me you have a bad cat. But there is a fix for that beside having to replace the cat... Just type into your Google browser and lots of stuff comes up
Type this How to fix a P0421 code ... Hope this helps you...
If this is the 2.4L or 3.0 engine, replace the upstream 02 sensor first and add cataylist cleaner, reset computer while driving for 25 miles, while making sure the motor is running correctly with all the other monitors setting like the O, OH, E, up until the C which should be triggered because of a drop of 5% efficiency in the pre-cat causing the code. If you live out of California this new exhaust manifold with pipes and pre-cat is $148.00 on E-Bay from Canada.
 

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If this is the 2.4L or 3.0 engine, replace the upstream 02 sensor first and add cataylist cleaner, reset computer while driving for 25 miles, while making sure the motor is running correctly with all the other monitors setting like the O, OH, E, up until the C which should be triggered because of a drop of 5% efficiency in the pre-cat causing the code. If you live out of California this new exhaust manifold with pipes and pre-cat is $148.00 on E-Bay from Canada.
The pre-cat has an upstream and downstream 02 sensor reading the pre-cat, so cleaning or replacing these 02 sensors sometimes corrects the problem because they are not reading correctly. But if you notice less air-flow from the tailpipe than the pre-cat has build up in it or if it rattles then a replacement is suggested. If the vehicle is not running correctly then the 02 sensors will read the difference causing the motor to hesitate due to no exhaust gases being able to get out of the pipe. There is an 02 sensor spacer found on E-Bay which can be put on to eliminate the problem temporarily. In California, if your smog is close to being required then you can go to a certified smog check station to have the state pay for the repair due to California Smog requirements not allowing 48 state legal products to be installed. If you replace the main cataylictic converter on any vehicle make sure it has ORD II stamped on it or make sure it is registered with the California Smog Board as legal for your vehicle.
 
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