you hook up the car to a SCANNER and read O2 sensor voltages.

the intrepid pre-cats have a stainless steel medium where the Expedition has a ceramic medium. When ceramic cats fail they rattle and break apart. Stainless cats don't do this which is why over and over again I'm telling you that diagnosis is important to determine the failure.

 

Well Im a professional I have expieriance, and I know for a fact that when a cat fails it makes a rattling noise,
you have a bad Oxygen sensor.

 

What you should do check the Voltage Values on the Oxygen sensors,
with your Scanner, you will determine if the Oxygen Sensor Values are within specs.

 

A professional would be able to spell experience. and I know for a FACT that the cats on an intrepid will NOT rattle when the fail because they do NOT use ceramic medium on the two light off cats. the 3rd cat does use ceramic. You must not be a professional Intrepid mechanic.

 

OK guys take it easy or take it to PMs. I don't want to lock this or make someone an example. Thanks

 

well m8s the shop GET IN GEAR told it was not my cat .. he test everything n it was my front oxygen sensor ..... he told when cat fails it would make a rough noise.. like my friends intrepid 1999... sapporro are you still here ????lol m8

 

a P0420 IS CATALYST EFFICIENCY FAILURE BANK1. I have cats that fail all the time and NEVER make any noise, no rattles no change in exhaust that ONLY happpens if the ceramic breaks down in the cat then you get that proble.

 

I have deleted posts and edited this thread. This is a technical forum. Take the silly side argument to PM. No exceptions.

 

I knew it was one of your Oxygen sensors, it wasnt the cat..

 

yeah you did help me thanks... mot like the other m8 was complaining abouth the spelling lol