Cheap man's ESS off button?

[AndySpill]

My question here is about understanding a JL Wrangler function, not building an easier or cheaper mousetrap to commercial tech to turn ESS off.

(Disclaimer: I'm a happy owner of the JL Tazer and Jscan, neither of which I use to turn ESS off. I run ESS events, have dual factory AGM batteries and my roof rack's solar trickle charging seems to have kept me from battery issues, fingers crossed.)

Before my question: most of you are familiar with relays: switches powered by one circuit (often one of far less power draw) that when energized close or open a second circuit used to energize some electrically powered device (hereafter an electrical appliance.) "Normally closed" relays only deny power to such appliances when the relay is provided power; normally open ones when the relay is not provided power. Vehicles have a fair number of relays and they can often be configured to operate either normally closed or open.

That said, take the ESS button on the dash. I'm guessing that it's a "normally open relay, with a manual switch," that can only close a circuit and light its button's light (signaling in turn further down the line to issue CANBUS messaging to turn ESS off when its circuit is closed with the button's push) when both the engine is cranked and a owner/operator presses that ESS off button. Turn the engine off and the ESS button's circuit opens, reenabling ESS (all other conditions for it to engage notwithstanding) for the next engine crank.

I haven't yanked it to observe, but why couldn't a simple device like this timed relay close the circuit that gets closed when you press the ESS button, https://www.amazon.com/Second-Timing-Timer-Multiple-Purpose/dp/B0CTFRT2YG?th=1, this linked device itself energized by some second circuit that flows power only when the engine is cranked, configured to wait a few seconds between successful engine crank and emulating the ESS off button press?

TIA

Again, this question's about understanding, not suggesting people who want to turn ESS off automatically save a few bucks and fail to instead acquire, for example, a Smart stop device to do this with CANBUS messaging.

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[GATORB8]

Here's the description, I'm looking for the diagram.

FUNCTIONAL DESCRIPTION - START/STOP DISABLE SWITCH
The Engine Stop/Start (ESS) switch is a driver select feature that permits the driver to inhibit the Engine Stop/Start feature. The ESS switch is typically located in a switch bank on or around the instrument cluster or center stack. The ESS switch is a smart device that sends two redundant input states to the Body Control Module (BCM) through a LIN bus circuit. The switch is a momentary press input, with the two states of the switch being pressed and not pressed. If the switch detects a circuit fault on either of the internal switches, a fault message is sent to the BCM for the faulty switch signal. The BCM passes the switch information to the Powertrain Control Module (PCM) over the CAN bus. The PCM uses this information for determining ESS system operation. The PCM also monitors for a stuck switch. If the input state received from the ESS switch is pressed for more than a calibrated period, the stuck switch diagnostic will fail.

The switch has a Light Emitting Diode (LED) to indicate to the driver the status of the ESS system. When the ESS system is active, the LED on the switch is off. When the ESS system is off or inhibited, the LED on the switch is constantly illuminated.

 

[GATORB8]

Is it in the center stack? (I don't have one) If so, looks like the communication is on the CAN bus, not binary 12V.

 

[AndySpill]

Thanks @GATORB8 but this leaves me wondering if the ESS off button is nothing more than one which closes a circuit, such that if I physically connected the wires that lead to the switch once the engine was cranked that I could turn ESS off that way.

Clearly, the method in which ESS is turned off is not as simply as closing a circuit, but rather, more likely, as you reference, that perhaps closing this circuit then in turn is one where "The BCM passes the switch information to the Powertrain Control Module (PCM) over the CAN bus. "

If I may make an analogy that I have no idea is accurate, when I turn my home air conditioner on I envision a series of steps unknown to me being undertaken to not simply first self test components, but start them up in a certain manner. But those behind the scenes steps might be agnostic to whether I turn on the factory switch, or connect/disconnect the wires manually that connect to it.

Then again, as you also write "If the switch detects a circuit fault on either of the internal switches, a fault message is sent to the BCM for the faulty switch signal."

Perhaps this suggest a situation where the switch is cognizant of attempts to tamper with it, and why designers of ESS off systems have found the easiest way to turn ESS off is not to tamper with the switch directly, but rather emulate the CANBUS messages that turning on the switch produces to turn ESS off.


Thanks.

 

[GATORB8]

Thanks @GATORB8 but this leaves me wondering if the ESS off button is nothing more than one which closes a circuit, such that if I physically connected the wires that lead to the switch once the engine was cranked that I could turn ESS off that way.

Clearly, the method in which ESS is turned off is not as simply as closing a circuit, but rather, more likely, as you reference, that perhaps closing this circuit then in turn is one where "The BCM passes the switch information to the Powertrain Control Module (PCM) over the CAN bus. "

If I may make an analogy that I have no idea is accurate, when I turn my home air conditioner on I envision a series of steps unknown to me being undertaken to not simply first self test components, but start them up in a certain manner. But those behind the scenes steps might be agnostic to whether I turn on the factory switch, or connect/disconnect the wires manually that connect to it.

Then again, as you also write "If the switch detects a circuit fault on either of the internal switches, a fault message is sent to the BCM for the faulty switch signal."

Perhaps this suggest a situation where the switch is cognizant of attempts to tamper with it, and why designers of ESS off systems have found the easiest way to turn ESS off is not to tamper with the switch directly, but rather emulate the CANBUS messages that turning on the switch produces to turn ESS off.


Thanks.

I'd think your SOL, brother.

From what I'm seeing, the switch is integral to the module, and that button module has a single digital CAN link to the Jeep's system.

 

[AndySpill]

I'd think your SOL, brother.

From what I'm seeing, the switch is integral to the module, and that button module has a single digital CAN link to the Jeep's system.

No worries. This was an exercise in understanding Matt through a theoretical implementation.

 

[kah.mun.rah]

The cheapest way to turn it off is to unplug the hood plunger.

 

[AndySpill]

The cheapest way to turn it off is to unplug the hood plunger.

....the cheapest way that doesn't cause the ESS off light (as the hood plunger method does) to appear in the dash that is, that is automatic.....

 

[X35]

The cheapest way to turn it off is to unplug the hood plunger.

Exactly, no ill effects other than the warning lamp possibly masking a depleted battery has been my conclusion to this issue

 

[AndySpill]

I think ( I say comedically) that I've been approaching this problem from the wrong side, as in address this problem from the business end of the ESS off button, not what goes on behind the dash.

I need to fabricate a 12V male plug that gets inserted in the console "cigarette lighter" female, connected to the afore-linked delayed relay, connected to a micro linear actuator like this that pushes the ESS off button to its off state (the button always being shut off, i.e. ESS on with each cold crank, start stop tech notwithstanding) a few seconds after successful cold cranking the engine.

Success will no doubt earn me top running in any of this year's Rube Goldberg machine contests.

In theory the cigarette lighter plug will grip its male counterpart with enough force to overcome the linear actuator's plunger.

(No, I will not be trying this.)

 

[kah.mun.rah]

....the cheapest way that doesn't cause the ESS off light (as the hood plunger method does) to appear in the dash that is, that is automatic.....

Everything that falls under the category "cheapest" will have its consequences. Manually messing with the electrical system could cause more bad consequences than a dash light but I like your ingenuity and thought process.

 

[T-VIS]

The ESS system is all CAN bus; it looks at factors like battery voltage, temps, etc, to decide when to enable the function when the vehicle is running, so technically it's all software.
Start/stop eliminators are available for purchase online, which essentially change the default position of the ESS switch from auto on to auto off.
I pulled the fuse and yeet'd the auxiliary battery because I don't want to deal with it.
https://a.co/d/b2vBiai

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