Hi everyone!

I've been having a problem with my Dodge's catalytic converter. It's been giving an error code "420 - Catalytic Converter Efficiency." I replaced both O2 sensors twice. I've replaced the cat with a Magnaflow High-Flo cat twice, each lasted maybe 3 months before the error code came up again. I then took it to a second exhaust shop that told me the Magnaflow did not work because it was only OBD I compliant and he put a Catco brand catalytic converter on it. Well it's been on maybe 2 weeks and the code has showed up again.

Has anyone else ever had this problem or know what's going on?

I got a 1999 Dodge Ram Sport with a new 5.9L 360 with maybe 5,000 miles on it and it's gone through the Magnaflow and Catco cat. It originally had a 318 for 140,000 miles and it went through the stock and Magnaflow cat.

Thanks!

 

Fix the plenum....... (see stickied plenum thread.)

What brand O2 sensors are you using?

 

I'm using Bosch 02 Sensors from Autozone.

Could the plenum be bad? I had the shop replace all the gaskets and got a new stock intake manifold when I had the new 360 put in my truck.

 

If they didn't replace the plenum gasket, it is probably bad.

Bosch O2 sensors suck. Our trucks hate 'em. NTK or Denso is the brand you want.

 

Read the plenum sticky as suggested, you will also find by doing so, that NTK or Denso O2's are the way to go. These rigs do not like Bosch o2's.