[gravitywell]

Yes, I know how it works, just what dealer/FCA states. How it works does not explain why it was designed however.

it's the "shift out of a forward gear (Neutral, then Park). These events are what turns ESS off because you no longer meet the criteria for ESS to be active"... which is the flaw in design. That "criteria" is just another way of stating how "it works".

My point is that there is a detectable difference between "stopped at a light-in Drive" and "stopped in parking spot-into Neutral" (or into R or into P"). so the "car cannot tell whether it's at a stop light or a parking spot" answer is no explanation.

Whether the reason that the car restarts when moving the trans lever out of the drive position is a software choice, or a choice in the electronics of the ECM or ESS, or whether it's inherent in the design of the engine or trans itself, the design ignores the differences enumerated above.

The events are the exact same, until you shift into Neutral, Reverse, and then Park.

1) In forward gear.
2) Decelerate
3) Come to a complete stop
*ESS On*
4)

At this point, the Cherokee, and the software has no way of indicating what you're next event is. If the next event would negate, or disable ESS, then ESS turns off, and your engine turns over again.

Your Cherokee doesn't know if you're about to pull away from a stop light, or shift into Park and go have a latte.

How would you propose ESS to predict your next event?

 

[Rojhan]

The events are the exact same, until you shift into Neutral, Reverse, and then Park.

1) In forward gear.
2) Decelerate
3) Come to a complete stop
*ESS On*
4)

At this point, the Cherokee, and the software has no way of indicating what you're next event is. If the next event would negate, or disable ESS, then ESS turns off, and your engine turns over again.

Your Cherokee doesn't know if you're about to pull away from a stop light, or shift into Park and go have a latte.

How would you propose ESS to predict your next event?

4) can fork two different ways:
4a) Hit the gas and keep moving
4b) Shift into neutral and potentially keep going into reverse and park.

In 4a) ESS should remain enabled
In 4b) It's a bit silly for a ~3 second restart of the engine.

4) while(brakes = applied); don't change anything

If you come to a full stop and ESS activates (shuts down the engine), and you put the car in park while the brakes are still applied, the engine remains off. If you take your foot off the brake, ESS starts the engine, regardless of what gear you are in.

While the brake is applied, you aren't planning on going anywhere. It's only after the brakes are released that the ESS decision should be made.

 

[Array]

I believe the root cause is the design of the ZF 9-speed transmission to auto-start very quickly. When ESS auto stops the engine, the transmission is still in 1st gear; ready to go.

"The 9-speed automatic transmission is also start-stop capable without hydraulic impulse oil storage (HIS). Since, in the case of restarting, it is only one friction shift element that needs to be closed, response times are indeed highly spontaneous."
http://www.car-engineer.com/the-zf-9hp-automatic-transmission-at-a-glance/

As the owner's manual states, moving the shifter out of Drive terminates ESS.

Conditions That Will Cause The Engine To Start Automatically While In Autostop Mode:
• The transmission selector is moved out of DRIVE.
etc......

When we think about it, when ESS is activated, the transmission is in 1st gear and applicable clutches (A, D, and F - http://www.wk2jeeps.com/Misc/Cherokee/KL_TSB/KL_RC_R01_15a.pdf) are engaged for a quick launch in 1st. Then the driver moves the selector to Neutral which requires Dog Clutch A to be released. That requires the engine be restarted to execute that dog clutch release.

That's my cut at it. I'd highly appreciate a Chrysler engineer familiar with the system to confirm or correct.

 

[Array]

....I guess I can just feather the brake more so it doesn't go into effect, but I always forget and then it goes on-off-on-off. ....

Slipping the shifter into Neutral just before the vehicle comes to a complete stop prevents ESS from activating and thus eliminates the on/off/on/off scenario. It amounts to the same as pushing the button on the dash.

The reasons I use the shift lever to solve the problem are two:

1) While stopping I often have my hand on the shift lever, or close to it.
2) I've driven deuce and a half trucks in the past and would shift into neutral at stops to keep from having to hold the strong clutch pedal down.

Give it a try if you like. After a while it becomes second nature.

 

[rpasetto]

The events are the exact same, until you shift into Neutral, Reverse, and then Park.

1) In forward gear.
2) Decelerate
3) Come to a complete stop
*ESS On*
4)

At this point, the Cherokee, and the software has no way of indicating what you're next event is. If the next event would negate, or disable ESS, then ESS turns off, and your engine turns over again.

Your Cherokee doesn't know if you're about to pull away from a stop light, or shift into Park and go have a latte.

How would you propose ESS to predict your next event?

Your logic is arguing against a point which I did not make? NO NEED to predict next event... to continue with your sequence...

"1) In forward gear.
2) Decelerate
3) Come to a complete stop
*ESS On* " [which means engine Off... OK if you're at a stop light... there are two possibilities for the next event...]
4)a. Driver lifts foot off brake engine starts and off we go...
..... or ....
4)b. Driver shifts to N and here's the design flaw. There is no need to restart engine, but that's what happens.

5)a. Sometimes the next step is to shift into reverse, if driver then lifts foot off brake, then and only then is an engine restart needed... just like what would happen in drive, in order to move the car.
...... or ......
5)b. Driver then shifts into Park and engine should stay off... for good this time f stop button is pressed.

So why is there concern with what the next event will be when trans is still in Drive with ESS on (eg engine off)? The next step is in fact completely evident as shown in the above... and my last few posts.

 

[gravitywell]

Your logic is arguing against a point which I did not make? NO NEED to predict next event... to continue with your sequence...

"1) In forward gear.
2) Decelerate
3) Come to a complete stop
*ESS On* " [which means engine Off... OK if you're at a stop light... there are two possibilities for the next event...]
4)a. Driver lifts foot off brake engine starts and off we go...
..... or ....
4)b. Driver shifts to N and here's the design flaw. There is no need to restart engine, but that's what happens.

5)a. Sometimes the next step is to shift into reverse, if driver then lifts foot off brake, then and only then is an engine restart needed... just like what would happen in drive, in order to move the car.
...... or ......
5)b. Driver then shifts into Park and engine should stay off... for good this time f stop button is pressed.

So why is there concern with what the next event will be when trans is still in Drive with ESS on (eg engine off)? The next step is in fact completely evident as shown in the above... and my last few posts.

If I haven't been able to explain that your car has no way of knowing of you're going to perform 4a or 4b, then there's no point in continuing.

Only one of those options breaks the on condition for ESS, and the Cherokee cannot predict which you're going to choose. ESS will no, and cannot operate while in any other gear besides Drive.

Read @Arrays description, as to mechanically why this happens.

 

[rpasetto]

If I haven't been able to explain that your car has no way of knowing of you're going to perform 4a or 4b, then there's no point in continuing.

Only one of those options breaks the on condition for ESS, and the Cherokee cannot predict which you're going to choose. ESS will no, and cannot operate while in any other gear besides Drive.

Read @Arrays description, as to mechanically why this happens.

You do not need to explain why the car has "no way of knowing" which action is next; that does not matter. My point is, and has been throughout this thread, that the engine should NOT restart when the shift lever is moved to neutral (eg step 5).

Yes I recall reading Array's description of the mechanical requirements, however like I said whether the software, electronics or engine trans requires the engine restart in neutral, there's a flaw.

 

[rpasetto]

The "requires the engine be restarted to execute that dog clutch release" condition, see earlier post#23 by Array, may be the explanation for the restart. Dog clutch A has to release to go into neutral, and evidently the restart in ESS is used as the way to do this. Whether this is because of a mechanical condition, required to have the necessary oil pressure to do the shift, an electric condition required to energize relays, or something else, this results in an undesirable result, specifically the unnecessary restart which certainly is a negative for engine wear, fuel economy and emissions. This is why I maintain that it is a design flaw. Whether this neutral shift could be accomplished by a mod to the ZF-9 trans design or whether a different trans design would be required to make these shifts with a restart, perhaps the right FCA engineer could answer.

Hopefully it is clear why the "ESS can't predict..." statement has nothing to do with the restart issue. That is the kind of thing I hear dealer service dept will say to out customers off.

 

[Rojhan]

The "requires the engine be restarted to execute that dog clutch release" condition

That makes sense from a mechanical viewpoint, but it sure is annoying from an operational viewpoint.

It sounds like having a human hitting the "A" button is the only workable solution.

Let's see.... splice into the button or one of the sensors (like the hood closed) that disables ESS.... Feed into a microcontroller that has GPS. Add various "geofence" locations, like your home and office, where ESS will automatically disable....

The other thing that might work would be to delay ESS/engine-off by 5-10 seconds. It defeats the purpose, to an extent, but would "fix" the issue as well as short red lights, etc. You'd need to find the actual output from ESS activation and put a delay on the leading edge of the waveform...

Having a full schematic, functional diagram, and theory of operation could make for some interesting modifications...

 

[mowcowbell]

I think the ESS function should be tied to the price of gasoline. When gasoline is below $1.50 a gallon (like it is here now), ESS is always off!

 

[rpasetto]

I think the ESS function should be tied to the price of gasoline. When gasoline is below $1.50 a gallon (like it is here now), ESS is always off!

Do not assume that ESS saves fuel all the time. It may when in traffic with long red lights, or under EPA test conditions... for sure not when driving in the country where the only stops are brief ones at stop signs.

 

[hexrays]

I'm growing somewhat accustomed to the ESS system, but my biggest pet peeve is how, when parking the car (in my garage for instance), the car will shut off and then start right back up when I put it in park. That, to me, seems like a complete waste. If I shift right into park, I would be happy if it would just stay in 'stop' mode so I can turn the car off. I guess I can just feather the brake more so it doesn't go into effect, but I always forget and then it goes on-off-on-off.

I'm a bit reluctant to make the change outlined here. Awesome work, but my lack of soldering skills and fear of violating the warranty will also likely make me just push the button.

As you approach your garage un-click your seat belt. It will disable the ESS.

 

[akguppy]

Bingo! ^^ Or in parking lots.

 

[rpasetto]

or just tap the stop/start button.

 

[crh8705]

Have you noticed that ESS is disabled when the low fuel light is on? This would lead me to believe it doesn't save gas.

 

[gravitywell]

Have you noticed that ESS is disabled when the low fuel light is on? This would lead me to believe it doesn't save gas.

It's more about emissions, than saving fuel.

 

[rpasetto]

Have you noticed that ESS is disabled when the low fuel light is on? This would lead me to believe it doesn't save gas.

It's more about emissions, than saving fuel.

There are a few conditions where fuel is saved, long traffic light stops, for example. In a drive with quick stop times there's no savings in fuel when a restart is done afet er a stop of only a few seconds. Restarts likely result in more emissions than a short idle time.

Certainly FCA was smart enough to run the EPA emissions test with and without ESS; you can rest assured the results were better using ESS

 

[Desoto]

One of the qualifiers for ESS is that "Flex Fuel Adapt" must be active. I don't have any ESS vehicles to play with, but if your not using E85 it just might disable the whole thing if disabled.

 

[Chuck1026]

I can't say that I hate the Auto Start-Stop engine feature on my Jeep; but I can't say I love it, either. I really just wish its function was inverted. In other words, default to not shutting the engine off and let me toggle it on when I think it would be beneficial. So after wrapping up my headlight mods last week, I've been thinking about how to make it work like I want.

So today I "fixed it". I modified my Jeep so that when I start it, the Auto Start-Stop ESS function defaults to off. At any time I can hit the button and toggle it back to on. Although not a difficult modification, you'll need a little soldering skill to be able to do this. If you're not handy with an iron, you either need to find somebody who is, or just skip this mod.

The basic idea of what I did was to simply install a solid state time delay relay configured for a single pulse output to drive a small dry contact relay that has its open contacts soldered between the dash pushbutton switch contacts. I tapped into the back of the Jeep dash power plug to power the time delay relay. I configured the time delay relay so that upon the application of power, it waits 1 second, then pulses its output on for just a moment, then back off again. It resets when power is removed.

It's really a slick tiny little relay that I picked up here:
http://www.amzn.com/gp/product/B00PD65UGA

You can see in the picture that I have the two configuration lines and the optional trigger line heat-shrunk off because at this stage, I had already configured it. That only leaves power in, ground, and switched output wires to hook up.

Ideally switched ignition power (only on when the engine is actually running) would have been the preferred power source to use. I spent a fair amount of time looking for such a power source, but wasn't able to find anything in the cab. So I decided to just use the switched accessory line from the back of the power plug. That accessory line also switches off during engine cranking, so even if you're sitting there listening to the radio with the car off and then decide to start it, the ESS is still toggled off correctly.

First I needed to tap into the power at the "cigarette lighter" power port. First, you have to remove the small rectangular piece of dash trim immediately above the console piece. It just pulls straight toward the back of the Jeep. I used a hook to get behind it and pull it out. Next, I reached my fingers into the gearshift boot and pulled the surrounding console straight up. It's only held in by a bunch of plastic latches. I was able to pop the gearshift pleather boot off of the console and lift the console over the boot to get access to the accessory socket to tap into the power and ground wires.

The next task is getting to the back of the Auto Start-Stop button. This is actually pretty simple. Just follow the face of the HVAC control panel as it curves away under the dash lip and find the bottom edge. Cram as many fingertips as you can into that thin lip and pull it straight rearward. The bottom two plastic latches will pop out. Then run your fingers along the sides of the HVAC control panel up as high as you can and pull the top two plastic latches out. Four latches and that whole panel comes right out. There's a 4-Pin connector to unplug and you can carry that panel into the house to work on.

A handful of Torx T-10 screws and two latches and the back of the HVAC panel will come right off exposing the circuit board. I was happy to see a whole bunch of in-circuit test pads all over the back of this board. Close inspection with an eye loupe shows that they tested this PCB on a bed-of-nails test stand because almost every one of the test pads has a tiny pin prick in the middle of it. Anyway, I found the rubber conductive membrane switch contacts for the ESS feature and discovered that one side of that switch is ground and the other gets grounded to toggle the switch. Further, the non-grounded side of that switch has a via nearby that routes the switch trace to the back side of the board and onto a test pad. This is perfect. I don't want to solder onto a via because of the rubber membrane on the board, but the test pad will work nicely.

A small gauge mod-wire on the test pad and a bigger 24Ga wire on the ground plane wired over to an electromechanical 12V mini relay and this part is done. The solid state time delay relay will toggle this mechanical relay.

I attached the white electromechanical relay to the PCB using double sided tape in an area where the back cover won't interfere (it has some webbing molded in to support the PCB). I knotted the relay power wires to act as a strain relief and covered them in sleeving and ran them through an existing hole in the back cover.

Finally, I programmed the time delay relay following the instructions from their website so that it waits 1 second and then pulses its output on for maybe a quarter of a second, then shuts it back off. That pulse drives the mechanical relay to simulate pushing the button. Further, if I wanted, I could even add a switch to this setup to break the connection between the solid state relay and the mechanical relay so that it would default back to "normally enabled ESS" operation. For now I'm going to drive with it like this to see how I like it.

This is awesome. I just was looking for a TDR last night and I bought the same TRD you selected! Thanks for the post - This will save me a ton of time and fix it to work as it should have been! Me and my starter thank you .

 

[NZOLIVER]

Hi all
I will do this and have a module in mind. Bit I will wait until it is out of warranty as if ANYTHING goes wrong with the control unit they will reject the claim!
There is an outfit in Europe someplace supplying a module just for this thing. They even have plun'n'play units for some VW and Porsche units I believe. More will be available i'll bet!!!
It is weird, as my wife's Fiat lets her keep the system switched off if she wants to (which she does )

Oliver