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New codes p308 & p1682 Needs some helpful advice

3K views 3 replies 2 participants last post by  dutch724 
#1 ·
I have 02’ 4.7ltr with 265,000 miles.
I recently had 2 codes come up. P1682 and P308. I have a partially clogged cat which I’m waiting for funds to replace them all.
I’m wondering if the back pressure from the exhaust caused my P308?
Anyway, I picked up the codes on the way to work one morning, on the same day on the way home the Jeep was working on overheating, but I was able to catch it and bring the temp back to normal with running the heat full bore. I had a couple of errands I had to do before going home the Jeep felt like it ran fine but I kept the heater running the whole time.
I’m not too worried about the P1682. The voltage gauge said the alternator was charging fine. I will have to run by Autozone to get it tested or just buy a spare so when it goes I slap the new one in and get wherever I was going. I have currently stopped driving the Jeep at least until I can get it fixed.
There is no water in the oil, So I’m not sure if it’s a blown head gasket. The last time I got a miss fire code it was a head gasket on the driver’s side, but the engine also hydro-locked (dead give away). With the overheating I just figured that might be the issue.
Any ideas where to start once the cats are replaced?
 
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#2 ·
The P1682 means the alternator is out I know because I just went through this. I can't understand how the gauge can be at charging with that code. When I got that code I had the system checked and it was not charging. You may want to pull lt and have it tested outside the car. That will eliminate any vehicle related issues that may effect that charging code.. I would not drive it until you get the overheating solved. As you know, these 4.7s are very sensitive to high temps and you an either blow the head gasket and some say, cause a valve seat to drop with just minor overheating.
 
#3 ·
This isn't the first time I have have had to replace the alternator. The first time the gauge just fell below charging levels and I got the old "check gauges" message. This time I was able to finish my drive to work and a few errands. The overheating issue is a big concern. I have stopped driving it. But I still don't know what could be the cause of the overheating. The only thing I can think of is a couple of weeks prior to this The belt tensioner seized and caused the motor to run hot until I could get stopped, but I figured if the temp gets to the engine destroying level it would cut off the engine and that didn't happen, nor did I wait for that to happen.
I still need to pull the #8 spark plug to check that out.
 
#4 ·
I think I have figured out what my trouble was with the codes and all the things that were going on.
I just replaced the whole exhaust system.... cats and all. The last cat was so clogged up there was hardly any exhaust getting through it. Which was why I had hardly and power and why the motor would run hot if I idled to long.
I can't explain the alternator code, but I checked it and it seems to be putting out the correct voltage. I will just keep an eye on it.

What I can't understand is why did the shop put on a huge muffler. I will attach a pic for everyone to see. If you know why please explain it to me.
 

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