My 2017 Cherokee WANTS me to get rid of it...

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32wildbilly
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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by 32wildbilly » Mon Sep 16, 2019 10:56 am

5chn3ll wrote: Mon Sep 16, 2019 10:28 am OK, here's the working theory, backed up by a ridiculously small amount of traction from teh Google: some OBD-II code scanners do not place nicely with the diagnostic ports on some vehicles. Kia, for example, has advised its techs to look for and disconnect OBD-II dongles, including code scanners and insurance company "good driver" trackers, because they can introduce signal degradation issues.

Multiple CAN-BUS errors will put the vehicle in "limp home" mode - there are several white papers out there explaining that the current bus implementation makes the system especially vulerable to attackers. I think my cheap-ass code scanner worked nicely as an "attacker" in our scenario. Interesting reading: https://rtcl.eecs.umich.edu/wordpress/w ... CCS_16.pdf
"Put it park" does not seem like a good limp mode to me!

This doesn't explain Dr. S's problem with the rental as I doubt he had a code reader or dongle(funny word btw) in the rental, but maybe the rental company does?

Has the jeep recovered from the issue?
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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by Dr_Strangelove » Mon Sep 16, 2019 11:25 am

32wildbilly wrote: Mon Sep 16, 2019 10:56 am This doesn't explain Dr. S's problem with the rental as I doubt he had a code reader or dongle(funny word btw) in the rental, but maybe the rental company does?

It was a Hertz rental - I wonder if they use nannies? They never sent me a nasty-gram for the speeding so obviously if there's a nanny they only look at the data if there's a wreck...
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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by Dr_Strangelove » Mon Sep 16, 2019 11:30 am

Here's my exact sequence for examination - we were re-arranging cars in Grandpa's driveway so it was a quick trip.

1) Car on - foot on brake - car in Reverse

2) Car backs out of driveway into road, come to complete stop, however, car stays in R with my foot on the brake while the other car pulls in.

3) Shift car into D hit gas - engine revs freely in "N" on dash (Shifter is in D), Car asks to be put back in P

4) Car goes back into P, error clears, I shift back into D, engine revs freely and says shift back into P.

5) Repeat same sequence 2 more times.

6) Car back into P, shut car off.

7) Wait a sec - start car back up.

8) Car goes into D, THUNKS hard, moves forward to driveway.


This is what made me think it was a software thing, more than anything..
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gnat
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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by gnat » Mon Sep 16, 2019 12:07 pm

I'm sure Hertz does install nannies, but they probably hard wire them in. I wouldn't have known that my Porsche dealer did it except that my foot got tangled in a mass of wires that suddenly fell from the underside of the dash while "briskly" driving down the highway. Called when I got back to my office and he explained what it was and to just shove it back up in the dash as best I could.

They've never said anything about my driving style ;)

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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by 5chn3ll » Mon Sep 16, 2019 12:17 pm

The "put me in park" condition is consistent with a common mode of transmission failure. My series of similar issues are not the same as Dr. S's, as his are all, I suspect, originating from the tranny. There's a sensor of some sort - Hall effect, I think, although I don't understand why one would be involved - that doesn't work right and the thing doesn't know what gear it's in, so it puts the car in neutral for "safety."

Then it reverts to the standard behavior for how you can put the car in gear - for safety.

This is DEFINITELY another instance where better coding could have tremendously improved both how the error was handled and the subsequent actions needed to get the car moving again (i.e. override the f*****g nannies if the speedo shows the car is moving so you don't have to park on the freeway)...

Dr_Strangelove (whew!) wrote: Mon Sep 16, 2019 11:30 am Here's my exact sequence for examination - we were re-arranging cars in Grandpa's driveway so it was a quick trip.

1) Car on - foot on brake - car in Reverse

2) Car backs out of driveway into road, come to complete stop, however, car stays in R with my foot on the brake while the other car pulls in.

3) Shift car into D hit gas - engine revs freely in "N" on dash (Shifter is in D), Car asks to be put back in P

4) Car goes back into P, error clears, I shift back into D, engine revs freely and says shift back into P.

5) Repeat same sequence 2 more times.

6) Car back into P, shut car off.

7) Wait a sec - start car back up.

8) Car goes into D, THUNKS hard, moves forward to driveway.


This is what made me think it was a software thing, more than anything..

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

Gone hunting with Alec Baldwin and Dick Cheney. Back soon.

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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by gnat » Mon Sep 16, 2019 12:45 pm

5chn3ll wrote: Mon Sep 16, 2019 12:17 pm This is DEFINITELY another instance where better coding could have tremendously improved both how the error was handled and the subsequent actions needed to get the car moving again (i.e. override the f*****g nannies if the speedo shows the car is moving so you don't have to park on the freeway)...
There is definitely lots of stupidity in car code (don't get me started about the (complete and utter lack of) security on the CAN bus), but this one is tougher. The issue isn't that the transmission may say one thing and the speed may something else, it's determining which to trust. Further than that, maybe it's not so much a mismatch as it has intercepted a signal to do something with the transmission that it knows should not be done (like shifting to 1st or reverse while doing 60mph down the highway).

If it simply flashed a message to the dash that said "fuck it, you're on your own!" and then the transmission proceeded to park itself on the highway while you continue moving forward, most people would be pretty pissed. Additionally, people would be quite pissed if their decision to keep driving because the system didn't scare them enough then resulted in a $5k+ out of warranty repair for a new transmission. So I get the design decision to limit their liability as much as possible even if I too don't really like it much.

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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by 32wildbilly » Mon Sep 16, 2019 12:57 pm

gnat wrote: Mon Sep 16, 2019 12:45 pm
5chn3ll wrote: Mon Sep 16, 2019 12:17 pm This is DEFINITELY another instance where better coding could have tremendously improved both how the error was handled and the subsequent actions needed to get the car moving again (i.e. override the f*****g nannies if the speedo shows the car is moving so you don't have to park on the freeway)...
There is definitely lots of stupidity in car code (don't get me started about the (complete and utter lack of) security on the CAN bus), but this one is tougher. The issue isn't that the transmission may say one thing and the speed may something else, it's determining which to trust. Further than that, maybe it's not so much a mismatch as it has intercepted a signal to do something with the transmission that it knows should not be done (like shifting to 1st or reverse while doing 60mph down the highway).

If it simply flashed a message to the dash that said "fuck it, you're on your own!" and then the transmission proceeded to park itself on the highway while you continue moving forward, most people would be pretty pissed. Additionally, people would be quite pissed if their decision to keep driving because the system didn't scare them enough then resulted in a $5k+ out of warranty repair for a new transmission. So I get the design decision to limit their liability as much as possible even if I too don't really like it much.
This is starting to sound like the Boeing 737 Max issue!
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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by 5chn3ll » Mon Sep 16, 2019 1:55 pm

Damned if you do, damned if you don't. Regardless, a fuggin' oil level indicator - since the oil level is obviously critical enough to shut the car down if it gets low - seems like a useful addition. Hell, even my 20-year-old water-cooled German abomination has one of those.

It seems pretty evident from my magazine-thick sheaf of printouts the service writer handed me that the Jeep's computer is not equipped logically to handle an impossible number of reported systems failures concurrently. I don't know what the various workflows look like; maybe this mess was already handled more elegantly than I'm giving it credit for, and I should be happy it went into limp mode instead of exploding.

Regardless, I'm now at the point where I'm less likely to just dump the vehicle. I'll look into a higher-capacity oil pan or some other way to increase the oil capacity. If I find one, I'm damn sure going to include a light that shows when the oil reserve needs to be refilled.

I'd been thinking about dicking more with CAN-BUS using a Raspberry Pi to see if there are any oil-related messages I can intercept myself and cook up my own oil level indicator, but the more I read about how fragile the bus is, the less interested I am in splicing into it.

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

Gone hunting with Alec Baldwin and Dick Cheney. Back soon.

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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by gnat » Mon Sep 16, 2019 2:06 pm

5chn3ll wrote: Mon Sep 16, 2019 1:55 pm Damned if you do, damned if you don't. Regardless, a fuggin' oil level indicator - since the oil level is obviously critical enough to shut the car down if it gets low - seems like a useful addition. Hell, even my 20-year-old water-cooled German abomination has one of those.
Don't give the German's too much credit. My significantly newer German abomination doesn't have a dipstick (though it has a tube for one :roll: ). To take it a step further, in their infinite German perfect wisdom they decided to make the oil check feature in the dash not work for 20 miles if the hood has been opened (say to change or top off the oil when you might really want to know what the level is...).

There is absolutely no more wonderful experience than performing your first oil change on your brand new $70k vehicle only to find that you can't tell if you've put enough oil back in or not until you go drive around for a bit (since the Durametric didn't have the PIWIS feature to clear the block)...
I'd been thinking about dicking more with CAN-BUS using a Raspberry Pi to see if there are any oil-related messages I can intercept myself and cook up my own oil level indicator, but the more I read about how fragile the bus is, the less interested I am in splicing into it.
Madness lies in that direction. I've long wanted to build a module to install into the P!g's bus that will do common sense things like allow me to close the hatch with my remote, roll the windows up and down from the remote, and remember the way I set features (e.g. leave the useless parking sensors turned off and sport mode turned on) across restarts. There is 4 metric crap tons of data flowing across the network and something like a RPi simply can't keep up if you want to do anything active (like listening for the remote unlocking the car, scanning for oil sensor messages, etc..). Then while the protocol is pretty well documented and actually fairly simple, what modules are on it and how they communicate is very manufacturer specific and completely undocumented.

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Re: My 2017 Cherokee WANTS me to get rid of it...

Post by 5chn3ll » Mon Sep 16, 2019 3:40 pm

Madness lies in all directions from where I'm standing...
gnat wrote: Mon Sep 16, 2019 2:06 pmMadness lies in that direction.
At this point, I'm in one of those trust-the-devil-you-know situations - so I think I'm just gonna hang onto it for a bit longer. Mrs. 5chn3ll does not feel safe in anything smaller than a Cherokee, and she doesn't want to drive anything bigger, and she still prefers Jeep. This limits my options to (a) driving what I already own, or (b) buying something exactly like it to find out if it's worse/different/better. B seems stupid.

My only preference would be to have another inch or two of ground clearance and another 50 HP or so. Still waiting for the right turbo kit to come along, but an incrementally more legit lift kit has come along. The aftermarket for KL Cherokees was pretty brutal when we first got the Jeep, but that's changing - I just picked up a "Rough Country 60400" 2" lift kit; that plus some spacers will let us run decent chains without tearing out the brake lines and ABS sensors.

60400-lrg-01.jpg
60400-lrg-01.jpg (33.17 KiB) Viewed 1879 times
Here's what 2" of lift looks like on a KL Cherokee:
42103-before-after.jpg
42103-before-after.jpg (101.63 KiB) Viewed 1878 times

Understeer: You will hit the wall with the front end.
Oversteer: You will hit the wall with the rear end.
Horsepower: How hard you will hit the wall.
Torque: How far you will move the wall.

Gone hunting with Alec Baldwin and Dick Cheney. Back soon.

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