Refer to Post #29 above. Is there a TSB for the relay issue?
Hi there,We are having the same problem with our 2020, either via remote start or in the car makes no difference. I'm convinced we have a junk battery but the service department isn't able to check it out till Friday. Checking briefly on a error code scanner turns up this "U0100 Lost Communication with PCM" which to me means that the battery voltage dipped too low during the starter cranking and caused a brown-out on the PCM computer, likely other onboard computers too because AlfaOBD shows a huge list of connectivity-related error codes.
It happened yesterday morning for the third time and my wife was in a rush so she left for work as it was with all the messages on. Car also started and died on her again when she was done with work, and she drove half an hour home and the battery only showed 12.0 volts when she got here, so I'm going with 95% certainty that the cheap worthless batteries they put in have let us down before we've even reached our second oil change. I suppose that more than likely I'll get a new battery from them when they check it out on Friday.
I know the service department is in full-time defense mode because they are buried with people having similar issues but I am not going to accept any form of the "oh, the battery cables were just loose" BS. Thats called getting "the runaround".
I asked them on the phone to get me a block heater to install on Friday too but they said the block heaters, or more specifically the block heater cords, are on backorder. Go figure.
I'll put a pigtail on and keep a battery charger on it the rest of the week. Low voltage to the computers is what I believe killed my Body Control Module that they had to replace in my Compass back when that one was new and having battery issues too. I know the real solution is going to be going and getting better brand batteries but I'm going to let them replace the OEM one once just so they can feel our part of the collective hurt they cause when they put crap batteries in new cars.
I could see relays as a possibility. The theory being that they "stick" when cold? Maybe.Well... to be honest, that doesn't sound like a dying battery to me. We've seen tons here on the forum, but your case brings different symptoms than what we normally see with low voltage events. I ran mine 8 months with a gradually dying battery and did not experience any of your symptoms, until the engine would barely turn over on cold starts. I'm not saying it is 100% not your battery, but... there seems to be a new pattern emerging with relays...
Good idea (for a get-by solution). I was actually thinking about one of these magnetic ones, they are sold in a farm and fleet store near-ish to where we live. Then I could easily use it on multiple cars or potentially even my garden tractors which have plows and snowblowers on them.Edit to add : for the block heater, not sure anyone on the forum has done it, but... how about a pan heater, perhaps temporary until you can get the real deal ?
Defective relays or replacing with better quality ones may well be the core solution. It makes sense.I'd say yes, judging from Thumpers posts. Same exact issue, it started right up and then died seconds afterwards. New relays installed and his problem was fixed.
Still doubt very much that the battery has anything to do with it. It certainly has no issue firing up the Jeep in that video posted.
The semi rapid 12.8V to 12.1V drop after turning the key to ACC is normal, many little sub systems are draining power. 12.8V resting is actullay good.Tried to get some more clues about our battery when I left yesterday afternoon but it didn't go perfectly smoothly so I didn't get any data that I trust. The Cherokee did start and stall on initial attempt and I think the stalling confused my cheap tester and it didn't record that result. The second attempt the car stayed running, on the tester it looked like a drop to about 8.2 volts on initial crank but of course the motor had just been started and ran for 3-5 seconds prior so you might say it was already "loosened up"... I don't trust my cheapie tester anyways but I like clues and data.
I will try not to be hung up on voltage but its hard not to note when its suspiciously low.
The timeline yesterday was that it had been on the battery charger all night on Tuesday night. Took the charger off Wednesday morning at 9 AM to put on another car. At 4 PM came out to it reading 12.0 volts, tried those crank tests, idled for 10 minutes and then drove it 10 miles into town. Drove it 10 miles home at 9 PM, and when I got home I turned off the HVAC, headlights, radio, etc etc. Shut it down and then turned back on to accessory mode. It went from 12.8 volts to 12.1 in the space of 2 minutes. At that point I just turned it off, got out of the car and went inside for the night. Doesn't seem like the battery should plummet to 12.1 volts that quickly, but I realize there are still a few electronics running even after turning everything else off that I could.
When the start-and-stall happened to me yesterday afternoon I did take note that like in the video it sounds like it cranks decently well and not for a long time, and also noted that it runs strong for a good 4-5 seconds before it shuts down. I agree that just listening to the time and speed of cranking it doesn't sound like a "bad" battery or that the motor is turning over all that hard. I'm building confidence in the relay theory. The battery may still not be a great battery overall but is looking less and less like the main culprit.
Tomorrow morning is the appointment for the service department to look at it. Its expected to be about -22F tomorrow morning. To ensure the folks at the dealership see the issue occur we are planning on dropping the Cherokee off in their lot this evening so it sits nice and cold all night. Then there is almost no way it won't demonstrate its little issue tomorrow morning (or so we hope). We're not going to leave the key for them because we don't trust that they won't try to move it before seriously looking for the problem and miss it while not paying attention. It will only do this issue once, maybe twice and after that its fine until it gets cold again, so we only have one shot to show it off.
Its going to be even a little colder yet Saturday morning, so we will probably leave it with them Friday after showing the issue and if they give me any balogna about "loose battery cables" (which I have obviously already checked for), I'll stop in early Saturday morning and see if it "fires right up". If they don't change anything on Friday then there is pretty much no way it will start up first-try on Saturday at -24 (so long as they park it outside).
Hopefully they will do an honest test on the battery, find its generally passable (although cheap and low quality), and then swap the relays which I dream they will magically have in stock (my dealer never has anything in stock, and everything is always backordered...) and that will be the end of it. If I pick it up Saturday and they tell me they changed relays and the battery is fine then I'll happily drive 3 more miles up the street to Batteries Plus Bulbs and ask them for a group 27F X2 AGM, and then I'll really be good to go.
We pretty much knew we would want to swap batteries before too long no matter what, as we do a lot of camping with a 12v compressor/refrigerator cooler in the trunk and want to be able to run that over a camping weekend without worrying about our battery too much. We were hoping not to necessarily have to swap batteries the very first year of having it, though. I already need to go buy one of those expensive X2 batteries to swap out the 4 year old OEM one on my Compass so the Cherokee was ideally going to wait a while, but, plans change.
Thanks for letting me do all my thinking out loud here, I'll post updates as we get it to the service department and see what they make of it.
I'll only agree to that if we add an asterisk that a "12.8 to 12.1 drop is normal for the OEM battery in Cherokees/FCA vehicles", surely none of you with a Northstar or X2 see such nonsense as a drop to 12.1 volts within two minutes of shutting the car down after just being driven? I would not accept a drop to 12.1 as "normal" after just shutting off the fully warmed-up vehicle for any other car with any other battery.The semi rapid 12.8V to 12.1V drop after turning the key to ACC is normal, many little sub systems are draining power.
To be clear, it did not "rest" at 12.8, I shut it off after driving all the way home and 12.8 was only what it read immediately after shutting the engine down, and only very briefly because within 90-120 seconds after that it was reading 12.1 with no lights, no radio, no HVAC blower fan, no heated seats or wheel, etc etc. That is not normal for any healthy, quality car battery.12.8V resting is actullay good.
You might enjoy reading this : Power-down current drawI'll only agree to that if we add an asterisk that a "12.8 to 12.1 drop is normal for the OEM battery in Cherokees/FCA vehicles", surely none of you with a Northstar or X2 see such nonsense as a drop to 12.1 volts within two minutes of shutting the car down after just being driven? I would not accept a drop to 12.1 as "normal" after just shutting off the fully warmed-up vehicle for any other car with any other battery.
To be clear, it did not "rest" at 12.8, I shut it off after driving all the way home and 12.8 was only what it read immediately after shutting the engine down, and only very briefly because within 90-120 seconds after that it was reading 12.1 with no lights, no radio, no HVAC blower fan, no heated seats or wheel, etc etc. That is not normal for any healthy, quality car battery.
Sure, I understand that the car doesn't ever truly "shut off" completely and that a little current is always being drawn, 30-600 milliamps or whatever, but even still, battery voltage is a reflection of the state of charge and the battery just cannot be 'healthy/OK' and also dropping to a 50% state of charge in the space of 2 minutes, right? That seems impossible.
For a reference point, yesterday after reading his post about 12.1v, I went out to my Jeep which had been sitting in a cold garage for 12+ hours and I got a reading of 12.5 volts under draw.Don't forget : resting voltage is not the same as voltage under draw. Your 12.1V was under draw. Remove battery from car, let it rest 8 hours at room temperature (70-ish), take resting voltage : if 12.1V, you are indeed below 60% SOC.