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2002 Concorde O2 confusion

I have a 2002 CHRYSLER CONCORDE LX. I pulled the trouble codes to find an intermittent problem with O2 sensor bank 2 sensor 2. I let it go for a while then began to receive an additional code for bank 2 sensor 1. So I replaced both sensors in bank 2. After which I no longer received any codes for sensor 2 but receive a high voltage code for sensor 1 with an additional code for random/multiple misfires. Assuming I received a bad sensor, I again replaced sensor 1 with no change. My mechanic is puzzled and so am I. Can anyone help?

So, if there is a DTC (diagnostic trouble code) for a system, such as the oxygen sensor system, you change a part because…? How did you know that the oxygen sensors were faulty? Were their performances in error? Or, did you just rely on the name of the circuit (oxygen sensor circuit)?
The DTC (Diagnostic Trouble Code) P0xxx, tells you what is wrong, and how it is wrong. All you have to do is to find out WHY?
Twenty five dollars ($25) a year will get you, or your mechanic, a subscription, for your vehicle, for a year, to repair information (including DTC troubleshooting charts). That’s much less than the price of an innocent part changed without evidence or a trial.
You’ve not told me / we the DTCs (codes). WE have the means to tell what they mean. We just need the codes.

I pulled the DTC’s that are currently being generated. They are P0300, P0152, and P0153. Does this help narrow things down any?

It helps to remember that the oxygen sensors are at the end of everything that’s going on in the engine. The oxygen sensors are affected by all the things that are wrong within the engine.
What the oxygen sensor looks like, when you remove it, can tell you some of the things that are wrong; such, as the engine burning oil, or coolant, or running rich. Look at your old oxygen sensors; it may be too soon to look at the new oxygen sensors.

DTC code P0153 is for “O2 circuit has slow response, on bank 2, sensor 1”. On an aged oxygen sensor, or one contaminated by coolant, silicone, or oil, this code will set.
You’ve replaced bank 2, sensor 1, twice! So, it’s not likely the sensor’s fault, is it?
Start your troubleshooting, and repairs, at the engine. There could be vacuum leaks, internal coolant leaks, burning oil, or burning silicone-based sealant. Go to this Web link for some pictures of “poisoned” oxygen sensors: http://www.sparkplugs.com/sparkplug411.asp?kw=Reading+old+oxygen+sensors&mfid=0 Go over to the stamp size image, and click on it for the oxygen sensor picture.

You need to do vacuum leak checks, internal coolant leak checks, excessive oil burning checks, compression checks, and fix the cause of the engine misfire. This article could help you find the cause of that random misfire: http://www.aa1car.com/random-misfire/
This Web link has some good instructions for some things to do and check. It’s 10 pages of helpful tips. Disregard that it’s labeled for “no DTCs”. It’s still what you need. http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528003ef98

I talked to my mechanic about what he checked on the O2 sensors. He pulled them and hooked them into some computer diagnostic system he has that monitors their performance. He didn’t find any problem other than a slightly slow warm-up time. Based on what he checked with his computer diagnostics there is nothing wrong with the car.