They are going to have fun with this.....

[ShadowsPapa]

2022 3.6 automatic, loaded.

Tuesday AM ding ding and the MIL lit up - checked and found these.........
And then yesterday and today every time I started it - ding, and MIL.
However, everything works perfectly.

And on this day, it started but for a moment I couldn't shift out of park -

So I have this kit that used to be used to fix the "idiot lights" in the 60s and 70s when the ALT light or oil pressure light would come on. You bought this kit and it could resolve the issues for you.
If they can't find and resolve the issue today, I'll dig and see if I can find that kit - oh, wait, here it is..........

The service writer asked "is the light on now" and I replied - if it's not, go out and start it again and you'll see it.
I originally made the appointment for the misfire issues but that happens so seldom, so far and few between, you can drive 4 weeks and not have it happen, or it can happen twice in one week. I went 2,000 miles without the misfire issue at all, then drove it another 1,000 miles and it happened twice - but it always comes right out of it with some RPM and a minute or two of time.
So I'm more hoping they deal with the above if they can only get to one thing today. Communication issues can leave you unable to shift or move, the misfire - you aren't dead in the water. It's just annoying.

IF hootbro sees this I know exactly what his response might be if he responds - and he'll be right.

The irony of it is that of all of the things I have done to, with or on this truck, all of the electric, the wiring, the mounting of winch and associated wiring, the mounting of the snow plow stuff and the massive amount of wiring involved, I've not even touched anything that involved any of the areas mentioned in the errors. The only things I've ever unplugged were the turn/park/DRL light connections up under the fender liners and the lights all are fine.

Anyway, hopeful it's something they've seen and dealt with before. Winter is upon us and my car gets parked as of this weekend.

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[Jefe1018]

Sounds like it’ll be the fun one to diagnose. I know that I made the mistake of unplugging the OBD-II harness once while the truck was running to hook up the pigtail to use JSCAN and it threw a fit with a bunch of error messages that all cleared themselves but nothing like this.

Now I comment to ask you sir, any regrets on moving to your new JT over the last one?

 

[ShadowsPapa]

Sounds like it’ll be the fun one to diagnose. I know that I made the mistake of unplugging the OBD-II harness once while the truck was running to hook up the pigtail to use JSCAN and it threw a fit with a bunch of error messages that all cleared themselves but nothing like this.

Now I comment to ask you sir, any regrets on moving to your new JT over the last one?

I'm so paranoid about that that I actually make sure the key fob is far enough away the truck can't detect it before I do any disconnects. I know it's silly, but that's just me.

No regrets so far. There are things like - this one doesn't do the mpg the other one did (even with the weight of the steel bumper and winch, the 2020 did better, but that's just being picky.
The only thing is - if they have trouble figuring out the CAN Bus communications issue and it turns into an on-going thing, or if that weird misfire only when the thing is totally warmed up, then sits for a few minutes and gets restarted - if either of those turn into an ongoing thing, I might ask my sales guy if they have sold my 2020 yet - LOL - I'm sure they have........ but he'll understand.
I think he's concerned as he knows we usually shop vehicles elsewhere and since he's sold me 2 in the past 3 years, I have a feeling he'll be an advocate if that's possible. (I didn't tell him that my wife got her last Grand Cherokee elsewhere - Motor Inn...........)

 

[BUZZHEAD]

Good luck PAPA ,if anyone can talk through their bs its you with your knowledge.

 

[ShadowsPapa]

Good luck PAPA ,if anyone can talk through their bs its you with your knowledge.

I already saw one coming - got a call from the service writer - he said the tech wanted to know what gas I ran in it. (related to the misfire - I hope LOL)
I knew what was up. I told him - the same gas I ran in my 2020 which never threw a CEL, never misfired, and the same gas my wife has run in every Grand Cherokee she's ever owned. 87 octane from Casey's or when I can, top tier gas from QT.
I told him "I go by the book, the owners manual" (I have run 88 on occasion as it's like 30 cents cheaper and I did run 91 in it while driving to FL as gas was dirt cheap where we were)
Then I told him - "well, the first time the truck has 157 miles on it and was running on the same tank of gas you guys put in it......."

LOL - I was thinking - so don't blame the gas unless you want that first one to be your fault!
157 miles was the first incident of misfire, on the same tank of gas they supplied me with.

Now if it had started this with a few thousand miles on it, I could maybe blame sticky injectors, carbon build up, whatever.

At least they can't blame the CAN bus electric problems on gas or oil or tires.

Question for modern IT guys who may also know CAN bus -
Is CAN closer to TCP where receipts or errors are acknowledged, or is it closer to UDP where data is sent and the sender has no way of knowing if it was actually received?

 

[Lost1wing]

I've seen multiple module communication fault codes turn out to be a bad battery. It was an escalade that was about 5 years old. It also had abs and airbag faults. Just one bad cell, but it started fine and every thing worked.

 

[OHJeeper]

Question for modern IT guys who may also know CAN bus -
Is CAN closer to TCP where receipts or errors are acknowledged, or is it closer to UDP where data is sent and the sender has no way of knowing if it was actually received?

I'm no CAN expert, but my understanding is that CAN is more like TCP with guaranteed delivery (though, not exactly like TCP) because it's used in systems that require high fault tolerance. LIN is a cheaper protocol used for things that may not need the higher level of fault tolerance (windows, dome lights) and is more like UDP.

 

[Summitsearcher]

Poor Hootbro. Papa’s got your number.

 

[Sandevino]

With a few exceptions, modern CAN networks in cars are start topology and use something similar to UDP. The master will communicate with the nodes (sensors) by polling or listening for responses.

Pulling a sensor will not immediately result in a fault as so many missed communication events have to occur.

 

[AmishMike]

Let's hope that the tech looks to see what all of those codes have in common, like a single power or ground point. I am guessing that most of them will fall back to something like that.
If they go after each one in order, well........Christmas is coming.
Good luck.

 

[RJinPV]

My first guess would be battery, but you know more about batteries than anyone else I've read on this forum. This will be an interesting thread to watch.

Edit: I'm sorry this is happening to your Jeep but on the bright side, maybe the root cause for this and the misfire will be the same.

 

[Elff]

After seeing this code

Maybe you just need to drop 1-3 Blue pills in the gas.
Problem is, the JT might not turn off for 12 hours.

 

[Sandevino]

I’d look for a toasty wire loom near the passenger exhaust manifold.

 

[ShadowsPapa]

I’d look for a toasty wire loom near the passenger exhaust manifold.

I thought that was for the diesels only.....

I was on my way to town to send off a sample of my zinc plating bath to be analyzed when my phone rang. This was about 2:30.
He said my truck was done and ready to be picked up.
So I dropped off the package and went to get my JT.

Right off the bat I'm skeptical that the CAN bus and communication issues I posted about above were resolved at all. I have a feeling it's going to happen again. But - it's been reported, I reported at least twice using email, and I got responses each time, so it's on record. (I did not see any reference to THAT problem - the CAN bus errors - on the paperwork. Not mentioned at all, not a bit.

But - they said that they found a TSB that described my misfire symptoms exactly in every detail.
So I'm hoping someone here has access to a Manufacturers Communication S2218000020
It will be in the form of a TSB.
What that TSB says is for the tech to check the CCDIFF NV EDGES data in the PCM
(that's where the cam/crank relationship is learned and kept. CCDIF is Cam/Crank Difference)
In the case of my truck, the values showed "not yet learned". So they took it through the learn cycle. There is now data there.
They were finally able to force some misfires by driving it and getting it good and warm, shutting it off for 30 minutes then monitoring the misfire data under light acceleration. There's a note that he could not get it to misfire in the stall.
They performed the cam/crank relearn and could not duplicate misfires again.

We'll see.............. but again, at least that's all on record now so no matter how long it takes, it's covered for that problem.
Same for the electric stuff above - I reported it, they had the truck, they had to see the codes when they scanned it and found "several P0300 codes stored" as stated on the papers.
So if it takes a year and it happens again, it will be covered.

I'd love to get my hands on that TSB for the misfire! It does sort of make sense - it was always 2, 4 and 6, never 1, 3 or 5 - the odds had some misfires but it was a really low count, single digits at most, often 0 or 1. But it was double digits for the even or left bank.

Now I'm going to try to get the electric bug to show up again by starting my truck every few hours after it's cooled off (that won't take long at 21 degrees tonight)

 

[Sandevino]

This diagram is for a JL but the connections are the same for the JT albeit in different physical locations.

The systems mentioned in the litany of trouble codes reference the transmission control module which feeds into connector XY313A in the diagram. Check this connector and ensure all connectors are clean and seated. Add dielectric grease while you’re in there. Next check the CSCIP star can connector and ensure all connections are good and add dielectric grease. The drivetrain control module feeds into this connection. Finally check the XY291A connector in the passenger fender well and add grease.

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