Just joined this forum and had same problem as you with the Automatic Stop/Start function.
In Nov 2019 purchased used 2018 Pacifica with 32000 miles. The engine S/S function (for saving gas in stop-and-go traffic) failed in January 2020 so I took it to Factory Service before 36,000 mile Warranty ran out to get a check-up and repair the S/S even though I do not like that function in a car that defaults to "active instead of defaulting to inactive due to location I drive in.
Service found the "auxiliary" battery at fault and replaced at no charge and is functioning for now; will see how long the new battery lasts.
The reason I purchased a used Pacifica was because of the "unknown quality" of all the gadgets on new cars and all the recalls - which I think is a rip-off on customers because most customers do not use most of the new gadgets and recalls should never become customary just so vehicles can be sold fast enough. I especially dislike the "subscribed to" gadgets that give me no benefit of owning that vehicle.
I replaced a 2002 T&C Lxi which I put on 265,000 miles from new and had no difficulties other than routine wear-and-tear of mechanical items; rebuilt trans 1 time, tune-up 2 times, A/C compressor 1 time and brakes 3 times. Yes it 'burned' some oil but within tolerance and usability. A very comfortable and long lasting minivan. As far as electrical items: a few light bulbs here and there.
Nothing like newer cars with all the electrical/software gadgets that fail all the time. I am an Engineering Tech and know from experience that electrical and software issues crop up at 'shut-down' or 'start-up' times mostly but mechanical issues are usually gradually noticeable during use at wear-out times.
Technology is wonderful except when it is not.
I will add that the 2018 Pacifica is no where near as comfortable as the 2002 T&C; mainly getting in and out of and long distance driving; but what do you do when family decides it is time to 'get-rid of the Dino' so they can get another car also.
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I hope this Pacifica lasts as long as the van.
This is a follow-up:
I took my 2018 Pacifica in for servicing/inspection to get a 'final' service before the 36,000 mile Warranty ends.
The Stop/Start (S/S) Battery was faulty and was replaced under that Warranty. According to the 'history' on that VIN it was the 1st time the S/S Battery was replaced. Can't really confirm since I purchased the van at 32,000 miles in late 2019.
Haven't been able to get a 'wiring diagram' for confirmation but it seems the S/S Battery is just a 'typical' Lawn Mower Battery with the posts in a particular location and size.
The technician did tell me I should be able to replace that battery myself after Warranty ends.
The OEM S/S Battery is quite expensive for just a small Lawn Mower type battery; probably just like most OEM parts are.
There were other issues I did not find answers for, and the tech didn't have either, and those were:
1. The Parking Brake would release sometimes when changing from Park to Reverse or Drive and sometimes it wouldn't.
2. The Parking Brake 'sometimes' would indicate, by light out, after shifting but the Brake did not release but upon pressing button the Brake would release. Still no definitive answer as to why.
3. The Hood has a 'small bit' of play in it when latched but I am still looking into that for some kind of adjustment I could make to tighten up the Hood when closed.
4. I am also looking for a 'uninstall' capability to completely get rid of the SiriusXm reminders in the van and in my emails because they are pestering me with "this is your final notice" again and again and again. I was taught the 'final' meant no more after that.
All in all the Pacifica is a nice van even though it does not 'fit' or 'sit' as well as the older Town & Country I had, and it has way too many technology trinkets that are just an expense and not needed to have a good vehicle. 'Technology is nice if it is useful and used but otherwise it is just expensive' for the customer and causes less customer allegiance to the brand.
This is what I call the S/S Battery function since most people will not use it or benefit from it and it was, apparently, incorporated to meet gas mileage requirements, or so I was told by Chrysler personnel, and causes customers to replace the extra battery every so often even though not wanted or used.
It seems that in today's market places more emphasis is being used to push technology trinkets just because technology can (seem to) do it even though technology is not necessarily as good or as reliable as an older tried-and-true method.
I have purchased many Chrysler products since 1967 but there is getting to be less reasons to keep it up or recommend it, especially for the expense involved.
I guess it is a good thing for the industry that their products are not like those in large chain and big box stores; satisfaction guaranteed or money cheerfully refunded.
Nuff' said
