Few codes, no CIL - advice

[relwell]

Edit - CEL not CIL. Was early...

Hey all - just looking for some feedback on a few things. Not a MegaJeepWrencherMan so will tackle the easy bits I know I can do.

Got a code reader app and b/t plug just to have a look at the Jeep. I didn't do that because I noticed anything specifically wrong, just had a feeling there would be something. Got a few codes back, P0038 and P0058 for the post-cat O2 sensors and a P0300 Multiple Cylinder Misfire. All stored. (Those O2 ones are from memory, will verify when I drive home today).

Before I consider a shop for plugs etc. I wanted to replace the easy stuff - crank and cam sensors for the P0300 and the post-cat (again, from memory so I will verify) O2 sensors for the P0058 and P0038.

There is no CEL so not sure if the PO just broke the light (which wouldn't surprise me) or if it would be best to clear the codes and see if they come back first - have heard that may not be the best idea for various reasons, but I trust y'all's advice.

So I guess my questions are:
- Is there any urgency on what to try first? Parts may have to come from the USA so lag times between parts may spike.
- Would one of these codes possibly cause the others?
- Should I just clear the codes and see if they come back?
- I also have an ongoing M13 noFUSE dash item as I am sure you all are not tired of hearing about. It comes back for about a week after disconnecting the battery and immediately blows fuses and then one day it will just be fine. I have searched all over for it but no joy. I don't think they're related at all, but can't hurt to mention again.

Thanks all!

[relwell]

Just to update while I am waiting for the engine to cool down so I don't melt my hands...

Cleared the codes, the P0300 didn't come back yet but all 4 O2 sensors show high voltage. S2b1 sensor reads 0 volts, 2 others read constant too high voltage and one does the right thing and fluctuates under 1 volt. Thinking it's odd all 4 sensors would be faulty so reading up on PCM right now. Seems TIPM could also somehow be involved which would be interesting with that recurring M13 fuse issue.

Once it cools down I'll check the no voltage O2 sensor connections and see if a little jiggle helps anything. Will give the others a look as well while I'm under there. Good news is without that P0300 I don't have to look for crank and cam sensors.

Just glad it's not freezing here in Canberra...

Will attach the code screenshot I snapped in case anyone wants to have a look.

[relwell]

Another update between rain storms. Got under and found the front driveshaft had eaten one O2 sensor wiring, S2B1. Solves one question at least of the 0V reading attached. One sensor does its job and oscillates. The other two sit at 1.27V consistently. Way too high.

Attached the wire pic and the live data for those who like pictures. Looking into PCM or TIPM still, just want more evidence before I spring for one of these monsters. Can't say what's weird electrically as I have that M13 issue which could be tipm innards related, or could be a short I haven't been able to trace yet. Had the tipm out and checked all the connections underneath. Some rubbing but nothing scary. The quest continues...

[Rod Harrison]

The two O2 sensors that don't oscillate are probably the wide band type sensor. They work in a completely different way to the traditional types.

Rod.

[relwell]

Finally gave in and took it to an electric auto shop. needed 3 new O2 sensors. One was shredded and the two 1.27V had ruined heater circuits.Surprising they can replace all 4 with OEM parts plus labor for cheaper than I could source the parts here myself and I will get a warranty, so they should be done with that soon. Hoping that clears the P0300 multiple misfire but will post here when I know more. Also asked them to have a look at my M13 issue but will see. Gladly pay to get the demon exorcised.

[relwell]

The update no one wanted:

PO had never done a service, apparently, as the spark plug gaps were enormous. And, shock of all shocks, the PO also managed to disable the check engine light. So that explains in part why this all came as a bit of a shock to me. Bought the jeep from a dealer across the country who swore it was checked up and down - lesson learned.

They replaced all 4 O2 sensors and the plugs. Idles better but the heater circuit is still FUBAR. But the likely culprit is the PCM and they don't think a little less fuel efficiency is worth that cost and trouble just yet. That and I would have to do it through a dealer and I just don't have the patience for that now. Everything will work when it warms up, just won't get the instant heat to the O2 sensors. Cool.

No word on the M13 fuse, but they're having a look today. I will get the jeep back tomorrow and see how it runs now. No codes, and the P0300 has gone away with the new plugs.

[Banshee]

Great progress!