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2005 Chrysler 300C 5.7L HEMI with 105,xxx miles. Check engine light decided to come on, so I scanned the codes and it showed that all four 02 sensors were bad. (P0038, P0052, P0058, & one more I didn't write down.) So, I made sure all connections were good and no exposed wiring, and I had replaced both downstream 02 sensors, erased the codes, drove it for a bit, and the check engine light decided to come back on. The codes were still showing that all four sensors were bad, throwing the same codes as last time. I tried replacing the front 02 sensors but didn't have any luck getting them removed. I figured it must be something else causing the codes anyway since it was still showing the ones that I had replaced were bad. I read that changing the spark plugs could fix the problem, so I changed all 16 spark plugs. (Side note: I did notice oil on a few of my old spark plugs, i'm assuming I have a bad valve cover gasket, But I don't think that would make my car throw an 02 sensor code) anyways, I cleared the code again and the same four codes still come on after I drive it for a bit. Has anyone else had this problem? Should I take it to a mechanic and get the front two 02 sensors replaced and see if that fixes all 4 codes? Could the oil in my spark plugs cause it to misfire and throw the codes? Could it be a bad PCM and need to be replaced?
 

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That one code that you did not write down was more than likely the real problem.
It is not uncommon for one code to trigger codes in other sensors.

Try unplugging the computer for a few minutes and see if it clears up, but get that other code first.
 

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That one code that you did not write down was more than likely the real problem.
It is not uncommon for one code to trigger codes in other sensors.

Try unplugging the computer for a few minutes and see if it clears up, but get that other code first.
The other code I didn't write down was the fourth 02 sensor. So it was the same problem, nothing different.
 

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You'll need to hook up a good diagnostic scanner that can read the O2 voltages and monitor your fuel trims. How does the engine run.....rich, poor fuel economy, stumbling, stalling, etc.? Besides the oil on some of the plugs (by the way where on the plugs was the oil......threads or on firing tip?), what did the plug's firing end colors look like? A good scanner (IMO, worth its weight in gold) should be able to check all of the engine management systems and give you some pretty good clues as to what is really going on. Good luck and keep us posted on your findings and fixe(es).
 

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here's a fix I just checked out for the 5.7 cat's...was getting codes P0130 andP0140.....both cats showing bad. new convertors..dealer $884 per side ....NOT DOING THAT !!!! previously replaced all 4 02 sensors....doing the do diligence thing , talked to a couple old friends, mechanic's....here is what worked........SEAFOAM , full can , 93 octane .....by the second tank fillup this AM , the check engine lite went out !! was told that if it didn't work to go to CAP or whoever you get your supplies from and ask for the screw in adapter for the rear cat 02 sensor( any sensor , remove sensor install adaptor and reinstall the sensor. What this does is pull's the rear sensor out of the full stream and allows a weaker signal to be seen for the difference between the fore and aft sensors'.. Chrysler's programing only allows for a small window up stream to down , and if it get's too wide , the cpu throw's a bad sensor reading code.
 

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here's a fix I just checked out for the 5.7 cat's...was getting codes P0130 andP0140.....both cats showing bad. new convertors..dealer $884 per side ....NOT DOING THAT !!!! previously replaced all 4 02 sensors....doing the do diligence thing , talked to a couple old friends, mechanic's....here is what worked........SEAFOAM , full can , 93 octane .....by the second tank fillup this AM , the check engine lite went out !! was told that if it didn't work to go to CAP or whoever you get your supplies from and ask for the screw in adapter for the rear cat 02 sensor( any sensor , remove sensor install adaptor and reinstall the sensor. What this does is pull's the rear sensor out of the full stream and allows a weaker signal to be seen for the difference between the fore and aft sensors'.. Chrysler's programing only allows for a small window up stream to down , and if it get's too wide , the cpu throw's a bad sensor reading code.
oh and the odometer just turned 100,888 miles and the check engine lite has been an off/on thing since 90k miles .
 
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