The check Engine light is on in my 2000 Honda Accord V6. The code is "420 Catl" or something, (I saw this on the little computer thing). After having my Cat converter replaced by a mechanic, the light came back on after a few miles. I had another mechanic put it up on his lift and look at the work done, and he said it looked as if the new Cat Converter was installed backwards, putting the O2 sensor on the wrong side of the flow. I desperately need to sell this car since my wife and I are having a baby, and I need that Light to go away! Can anyone help me?

 

The O2 sensor goes to the rear of the converter, if it's backwards go back to whoever put it on wrong and tell them to fix it.

 

Should I just tell that mechanic that other mechanics said he put it in backwards? Also, is there a picture source you can point me to so verify that?

 

Thanks! I looked at it again and the sensor is definitely not behind the Cat, it's before the Cat has any effect on the exhaust. I'll show him the picture and get him to fix it.

 

You really shouldn't have to show a "mechanic" an image of where the secondary O2 is located. It is always located after the cat. It doesn't matter if it is an import or domestic vehicle.

In this case he will have to take it out and turn it 180 to put the O2 at the rear. It should be an easy fix. As long as it is a bolt in cat and not one that was welded in place.

 

I'm going with weld in, I've never seen Honda use the same type of flanges on both ends, they're pretty good at making things idiot proof most of the time.

 

Ah yes...this is true!

OEM uses a 2 bolt socket flange in the front and a 3 bolt flat flange in the rear IIRC. It would take some work to put it in backwards.