I've got an 05 with the 3.7, 124,000 km and have been having trouble with my check engine light coming on and off for the last few months. The last few times I had it scanned it was coming up p 0420 - cat converter as well as an o2 sensor. Well the cat was replaced as well as two of the o2 sensors. I am still getting the code for the cat plus a new one the P 2096 which is down stream fuel trim lean bank 1. The vehicle seems to drive fine and my gas mileage is back to normal after getting the new o2 sensors and the cat, any ideas as to why I am getting these codes.

In most cases with Chryslers it's caused by the use of aftermarket parts.Bosch O2 sensors do not play well with Chrysler PCM's(NTK or Denso used for OE),and aftermarket cats mixed with OE cats will always cause MIL issues in Chrsylers.

I guess I should have mentioned that all the work was done at the dealer. They suspect it's an electrical issue but are unsure at this point.

The dealer reset my cel again on tuesday and it came back on today, but I noticed a misfire and loss of power for a few seconds before the light came on. It was doing this about 4-6 months ago but stopped after running some amsoil PI through it. This time it's going in to be scanned before I do anything else. Man this is getting tiresome though, I should have stuck with my cherokee! These Liberty's are junk!!!

Well, after another two trips to the dealer I think they have finally figured out what was wrong. They replaced the two remaining o2 sensors, so as it stands now all 4 sensors plus a new cat and the engine light has been off for 5 days now. This is the longest it's been off in the last 6 months.

I forget which codes it was pulling but one of our liberty's here at work, an 05, had an issue all of the sudden it just died on the road. Towed back, it would start up and then stall out, turns out it was clogged cat. Dealer replaced under emissions warranty, but we still had a CEL. There was a TSB on the valve spring retainers so they were replaced not by the dealer. Heads were all check out and everything was all good. Still, CEL, and it was something to do with the cam position sensor. The reason the cat originally went bad was unburnt fuel was being expelled out of one of the cylinders and getting onto the cat and burnt it up/clogged it up.

After my mechanic gave up and sent it to the dealership, they re-replaced everything that my mechanic had done, plus replaced the cam shaft....yes, the f'n cam shaft!! My mechanic was like "I duno what it is, it doesn't make sense unless the cam shaft is screwed up, but it's got like 75 or 80k....camshafts don't just break." Well, apparently the lobes on these cheap-o cam shafts can turn and cause a problem. Thing has been fine ever since, but it would have been cool if it never happened. Of course the work wasn't covered under warranty....internal motor parts that were damaged not from abuse or neglect....just bum luck.

On the other hand, my wifes 04 has 170k on it (knock on wood) and runs like a top.

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Civilisation exists by geological consent, subject to change without notice. -Durant

I'm not sure if my cat was plugged or not, the vehicle still had it's normal amount of power but it had a slight misfire once in a while. I would not have suspected the cat was bad if the dealer did not say so. It was covered under the emissions warranty as well.

See if you can find out more about what was wrong with the cats....

If you CEL stays off, maybe you're good, but why on earth would a cat go bad?? Something needs to happen to make it go bad. Just saying. I believe we had a cylinder misfire code still after the cat was replaced. It ran fine after replacing the cat...just had a CEL on. It eventually would have ruined the new cats if we hadn't fixed it.

I hope you're not having the same thing happen to you!

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Civilisation exists by geological consent, subject to change without notice. -Durant

Check engine light is still out and the misfire seems to be gone as well. I'm not sure if a bad o2 sensor was the cause of the misfire or if it is something else that actually caused the misfire which then caused the cat and o2 sensors to go bad as a result. Time will tell I guess.