2004 Grand Cherokee - Replacement O2 sensor and catalytic convertor

[joshua_msu]

How much can I expect to pay to replace these parts? After replacing the PCM at my dealer, my original knocking problem was fixed, but alas the check engine light is back on. They are quoting a price of 600 to replace both. Im sure can get better from a local mechanic, but just wondering how much better can i do? Is there any harm if I don't fix either of these two items? Thanks.

[riverat440]

I don't understand why you want to change both at the same time. Unless you have emissions to pass or the cat is clogged would be the only reason to replace the cat. You didn't mention whether you had any codes or if the MIL was on but each of these have their own codes and unless there is a O2 code don't waste your money replacing it either. If there is an O2 code it would be a good idea to replace it as it has a lot to do with performance and gas mileage.

[joshua_msu]

Originally Posted by riverat440

I don't understand why you want to change both at the same time. Unless you have emissions to pass or the cat is clogged would be the only reason to replace the cat. You didn't mention whether you had any codes or if the MIL was on but each of these have their own codes and unless there is a O2 code don't waste your money replacing it either. If there is an O2 code it would be a good idea to replace it as it has a lot to do with performance and gas mileage.

I took it back to the dealer two days after replacing the PCM since the check engine light came back on. They ran the codes, and said either it could be a bad catalytic converter and or O2 sensor. They quoted me that price which seemed a bit high.I have no emissions to pass here in Michigan. I haven't really noticed a change in performance or gas mileage. Obviously something has failed in order to cause the light to come on. Thanks for the reply.

[fredjacksonsan]

O2 sensor you can do yourself, it (or they, if you have one before and one after the cat) simply screw into the exhaust and have a snap connector to the wiring harness.