[Bob Lincoln]

Well, a broken exhaust stud could eventually allow it to develop a gasket leak. I'd fix the stud anyway and then clear the codes and recheck them.

"P0420 Catalyst System Low Efficiency" - this can be either a failed catcon or, more likely, a failed downstream O2 sensor.

How does it run?

 

[mopar56]

he said performance is good but it did have a bit of a stumble once at a traffic light today, I am in the marine business some outboards use o2 sensors and they can be tested buy heating the sensor with a tourch and pinning the leads with a volt meter and checking with origanal specs, is there such a test for this one?

 

[Bob Lincoln]

I've heard of people testing them with propane, but that's not an accurate test. Best way is to use an oscilloscope and watch the output change back and forth across the center point at something like 8 times a second. Slow or mostly off-center or reading near one end of the scale is grounds for replacement.

 

[mopar56]

well if it turns out that we end up replaceing the cat has anyone used one of the magnaflow ones?, do they add any performance?