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Discussion Starter · #1 ·
Howdy y’all,

so I’ve read a ton of threads so far about PTU issues and exc. Ill give y’all a run down and would love to see what you think.
The beginning
2019 Jeep Cherokee Trailhawk 93k

-New tires installed Thursday 5/16 (same 65r17s but a little more meat prob a acouple lbs heavier than stock destination AT2)
-Trailer wiring harness installed Friday morning 5/16
-Little road trip (4 hrs) to pick up 750lb trailer
NO ISSUES NOTICED
-Oil change Monday afternoon.
- Tuesday morning notice SVC 4wd icon display. Begins as a solid icon then only came on intermittently with sharp turn or something like that.
TODAY
Retrace steps (mechanics/shops) who worked on car. Typical “we did nothing wrong it’s a coincidence stuff”
After chatting with trailer shop who installed wiring harness I see that they did not hook harness directly to + battery terminal (they stated that there was live wire underneath, I suspect they tied into something). I make them rewire it. Icon still coming on intermittently. No dealership will throw me in diagnostic for 2 weeks minimum. No active codes being thrown. Stored code for PTU but even when SVC4wd icon is displayed no codes being thrown.

Plot twist:

When I drive home from DCJ dealership I decided to throw it in both “sport/snow” to see/feel power difference on the selec-terrain system. Entire 30 min drive home no SVC 4wd icon drives normal everything seems fine.

Side note: Leaving Friday for 4000 RT mile road trip to Idaho for camping and exc pulling 1000lb trailer.

What y’all think?!
 

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Sport mode is not going to do anything different other than keep the ptu in awd mode, vs fwd when it speeds up. How old is the battery? Its possible maybe your battery is older and they ran down the battery with the doors open and such. Then as you drove it more it recharged the battery and your issues went away. An older battery would be more susceptible to this. Just a thought. Also, you didn't mention what tires you went with. Did you go up to an LT tire or keep a P rated tire? Its hard to say without knowing the code, or being able to monitor while the ptu shifts.
 

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+1 on the battery ^^.

@AustinKL19 : battery health issues are easy to identify via ESS (engine stop/start). If you've had ESS not working lately, with a ''Stop/Start disabled Battery Charging'' message, then there is the problem (battery). Some people disable ESS continously or use a module to disable it, thus removing the 'natural hability' of the system to warn of battery health issues.
 
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Discussion Starter · #4 ·
+1 on the battery ^^.

@AustinKL19 : battery health issues are easy to identify via ESS (engine stop/start). If you've had ESS not working lately, with a ''Stop/Start disabled Battery Charging'' message, then there is the problem (battery). Some people disable ESS continously or use a module to disable it, thus removing the 'natural hability' of the system to warn of battery health issues.
New tires ALL TERRAIN T/A KO2LT245 /65 R17 111S D1 RWL

battery was replaced semi recently but will go get it tested
 

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Discussion Starter · #5 ·
+1 on the battery ^^.

@AustinKL19 : battery health issues are easy to identify via ESS (engine stop/start). If you've had ESS not working lately, with a ''Stop/Start disabled Battery Charging'' message, then there is the problem (battery). Some people disable ESS continously or use a module to disable it, thus removing the 'natural hability' of the system to warn of battery health issues.
ESS seems to be working as normal. Ever since engaged in sport/snow I haven’t throw icon. Also took out last night and didn’t throw SVC either. Super intermittent.
 

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New tires ALL TERRAIN T/A KO2LT245 /65 R17 111S D1 RWL

battery was replaced semi recently but will go get it tested
Thats wierd. They don't list the LT version in that size on the website. They do have a P version, and its only 2 lbs heavier, so thats not much.
 

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ESS seems to be working as normal. Ever since engaged in sport/snow I haven’t throw icon. Also took out last night and didn’t throw SVC either. Super intermittent.
If ESS is working Ok, battery is likely not a problem here.
 

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Discussion Starter · #9 ·
Sport mode is not going to do anything different other than keep the ptu in awd mode, vs fwd when it speeds up. How old is the battery? Its possible maybe your battery is older and they ran down the battery with the doors open and such. Then as you drove it more it recharged the battery and your issues went away. An older battery would be more susceptible to this. Just a thought. Also, you didn't mention what tires you went with. Did you go up to an LT tire or keep a P rated tire? Its hard to say without knowing the code, or being able to monitor while the ptu shifts.
When I have selec-terrain in auto that’s the only time the SVchshsh
Sport mode is not going to do anything different other than keep the ptu in awd mode, vs fwd when it speeds up. How old is the battery? Its possible maybe your battery is older and they ran down the battery with the doors open and such. Then as you drove it more it recharged the battery and your issues went away. An older battery would be more susceptible to this. Just a thought. Also, you didn't mention what tires you went with. Did you go up to an LT tire or keep a P rated tire? Its hard to say without knowing the code, or being able to monitor while the ptu shifts.
the SVC icon is only displaying when in “auto” mode on selec-terrian. From my understanding it bounces back and forth between FWD and 4WD depending on “need”. When engaged in sport/snow/sand/mud it should constantly engage the PTU correct ? From my observations it like there’s some miscommunication with PTU when engaged in auto mode.
 

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When I have selec-terrain in auto that’s the only time the SVchshsh

the SVC icon is only displaying when in “auto” mode on selec-terrian. From my understanding it bounces back and forth between FWD and 4WD depending on “need”. When engaged in sport/snow/sand/mud it should constantly engage the PTU correct ? From my observations it like there’s some miscommunication with PTU when engaged in auto mode.
That is correct. It will not go to fwd in any of the modes other than auto. Also, manual shifting will also keep it in awd. It doesn't go to fwd until like 25ish mph and ligher throttle. Anything more than like 75% throttle will also reengage awd. When coming a stop, it is lower before it goes back to awd.
 

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Discussion Starter · #11 ·
That is correct. It will not go to fwd in any of the modes other than auto. Also, manual shifting will also keep it in awd. It doesn't go to fwd until like 25ish mph and ligher throttle. Anything more than like 75% throttle will also reengage awd. When coming a stop, it is lower before it goes back to awd.
So to me it doesn’t sound like anything is truly wrong with the PTU. If I’m still receiving proper power and capabilities under the other modes when 4wd is engaged then it sounds like some communication issue within the “auto mode” as it decides back and forth between the 2. I’m not having as much anxiety as before. I’ve been driving all day testing between manual “auto”, snow, sport and haven’t had a single notification display. I’m not exactly sure where it leaves me but I’m head West in the AM for Idaho MTN adventures so wish me luck y’all!
 

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So to me it doesn’t sound like anything is truly wrong with the PTU. If I’m still receiving proper power and capabilities under the other modes when 4wd is engaged then it sounds like some communication issue within the “auto mode” as it decides back and forth between the 2. I’m not having as much anxiety as before. I’ve been driving all day testing between manual “auto”, snow, sport and haven’t had a single notification display. I’m not exactly sure where it leaves me but I’m head West in the AM for Idaho MTN adventures so wish me luck y’all!
Just a long shot and easy to check : make sure the battery connectors are nice and tight. Try twisting them by hand : of one moves, it's loose. Loose connections can and will cause all kinds of weird problems on these Jeeps...

Wishing you a safe and great trip :)
 
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