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Hello, I am new to the commander world - just purchased a 2006 3.7 4x4 with 91k miles. Got a stack of receipts with it from the dealer and local Pittsburgh shops back to 2009 - pretty cool, that almost never happens when I buy a used jeep. In addition to my new commander, I also have 4 XJs and 1 MJ (all 4.0L). Looking forward to joining the community.

I am also having trouble getting to the bottom of the issue I have been having for 1+ month since buying the Jeep and would appreciate all the help I can get! Here's the background and where I am at:

The guy I bought it from said he was having flashing engine light and traction control light. It didn't happen when I test drove it, but started to happen intermittently after a few days of getting it home (seemed to happen when cold) but would be ok when it warmed up. Then it started getting worse, gas mileage is at about 10 - 11 mpg (hope that's not normal haha) and I was getting random misfires P0300 and occasionally a P0302 but no permanent engine light yet just the misfire after cold start still. I also occasionally smelled burning rubber/plastic smell from the engine bay that I figured was from the bad AC compressor but I removed the clutch relay and still happened - smelled electrical to me. Then after a week or so I started getting P0152 B2S1 O2 sensor high voltage. So I changed the plugs, coil packs and all sensors I could think of that could be involved (TPS, IAC, MAP, IAT), new ASD relay, and two new O2 sensors on Bank 2 with NTK sensors (B2S1 with Part # 23160 and B2S2 with Part # 23159) and cleared codes. Checked all fuses in the engine compartment (doesn't look like there is an o2 sensor fuse which is a little alarming) Misfire still was happeneing and actually got worse - it started happening when I was driving on the highway and P0152 and P0052 kept coming back immediately. I could also still smell the burning and it seems to be coming from the right firewall area where the PCM is (but also under where the sensor is located so hard to tell). I noticed water from the hood seal dripping on the PCM and it looked like it's been happening frequently which is not great (what a terrible place to put it btw). Seems like the PCM could be where that burning smell is coming from but I can't be sure. Checked freeze frame and Short term fuel trim was very rich for bank 2 ( -32.8) and the o2 sensor is stuck on low and won't let the jeep get into closed loop. So I changed the PCV valve, cleaned the throttle body, tightened the intake manifold, and new injectors on bank 2 just in case and cleared codes and battery disconnect for 1hr etc. Misfire seems to have gone away so far but same O2 codes. I then monitored the O2 live data again with my scan tool and at first the heater voltage was 0 but now it's back working randomly and P0052 is gone. The sensor voltage reads very high but does change slightly - it hovers around 4.95V or 2.45 on the 0-1 scale which is obviously very high. B2S1 connector is wedged way up there inbetween the trans dipstick (which was a huge pain to get off btw) so it's near impossible to check the wires for cuts without dropping the trans which I really do not want to do. I also checked and cleaned the PCM ground. The ground strap on the engine looks rough, but I can't see where it goes to in the back behind the firewall. Other thing I noticed last night while monitoring the live data was the coolant temperature was sitting around 185 and 190 for the longest time while idling in the driveway. I unplugged the sensor while it was running and then plugged back in and it stayed constant for a few minutes then decided to go up and up until it got to 208 which is more where I expected it to be after idling for 30 mins). I also checked the rest of the modules for codes and this is what I found stored: U0401 on ABS module, B162B, C121C, B1239. I cleared them and haven't seen them come back up yet but that's not to say they won't. At this point, I am thinking it could be ground related but I am getting closer and closer to condemning the PCM as well due to the erratic data I am seeing on the scan tool, the U code above, and the burning smell/water on it, lack of fuse for sensor, etc but I would love for any more suggestions on what it could be and if you think this is a logical next step.
 

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Discussion Starter #2
FYI if anyone is interested, I unplugged the O2 sensor and re-plugged it back in and it cleared the codes. Since that sensor plug is so tight, it must not have been plugged in all the way.
 

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Hey bud. Next time try using the search engine. I had probably the same symptoms a few years ago with 5.7 and unfortunately chased through the cam, crank sensors, coils, plugs etc. and then moved to the O2 sensor on the list. Turns out it was pooched. It also had to be the one tucked up by the trans dipstick that takes an act of God to unplug and plug a new one in.
 
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