So here's an interesting one. First a little back story..

I recently had my 2014 GT at Ford to get the airbag recall done, an oil change, and new spare key fob programmed. The lady at the desk told me the tech grumbled about the key programming being difficult and she thought he said something about an aftermarket computer. My ECU is factory, but I do have a tune on it so I thought maybe the tech could tell somehow but whatever...The car drove home fine and sat for a couple weeks.

Without having started the car since then, I installed a new 1-piece driveshaft and BR shifter bracket/safety loop, straight forward nothing crazy (or electrical) involved. When I went to start it after my battery was dead. No big deal, put my jump box on it and it lugged a little but started up. This is where it got weird.

ALL of my gauges started momentarily but continually dropping toward 0 then picking back up, and warning lights started blipping on and off with the doo-do-doo chime over and over, almost like everything was momentarily losing power and resetting randomly. The info screen kept cycling through messages indicating zeros/lost information, like "--- miles to empty" etc. But when the actual reset happens I get a very quick "check charging system". The car runs and drives normal otherwise, and no codes on my scanner. Also, the screen on my radio is blank and my climate control lights don't come on - BUT the radio plays music and heat comes on like normal.

So, I checked the voltage on my battery, 12.xxV while off, 14.xxV while running, seemed ok but just to rule it out I put a brand new battery in it. Now 12.9V off and 14.73-14.76V while running, with rpm fluctuations and electrical load changes, from all lights/accessories on to everything off. So it seems like the alternator is fine, and at this point I'm really hoping the Ford tech didn't do something to mess up my ECU or some other control module. Then, I notice one more thing. The issues ONLY happen when the engine is running. When it is key-on engine-off, there are no problems. No flashing warning lights, no chimes/resetting, the radio display works, the climate button lights work, all is normal. Then, as soon as the engine is running, the issues begin again. I tested these two separate states multiple times and it is consistent.

Without knowing this car's electrical system very well, I'm assuming the main difference between KOEO and KOER is the alternator. So even though it seems to be charging consistently and I couldn't SEE any spikes or drops on my meter, I'm hoping that's what's happening and it's just super fast or something. I've ordered a new one and we'll see this weekend.

Just wanted to post this to see if I get some agreement, or if there are some other common gremlins people might think of, like BCM issues or something. For the record, it was down-pouring the last time I had driven it before this, and that was the first time it's ever seen rain in my ownership, but it feels dry on the passenger floor and behind kick panel.

Thanks,
Eric

PS: This is my first post on these boards, so hello and thanks! I have a 2014 Mustang GT, intake/exhaust/tune. Previously had an 89 GT hatch FBO, 49 Ford pickup, 94 Dodge Stealth with fully built VR4 swap and some other toys. I'm a robotics engineer by day and have been a gear head my whole life, a jack of all trades but definitely master of none, so I'm always super appreciative to learn from everyone here!

 

The voltage regulator inside the alternator is obviously fine but it may have at least one diode that's causing a small AC current to leak into the main wiring harness. Perform an AC ripple test (there are videos describing the procedure in YouTube) before you start throwing parts at the problem.

 

Cool thanks, I didn't know about this test. I gave it a quick try on my way out for work this morning and only got 0.023 VAC, but of course the car was not showing any of the problem symptoms either. I'll have to give it another try later when I have more time.

 

It's likely you battery management system. Have a look at this site. https://www.mustang6g.com/forums/thr...-reset.106897/
Lot of times like with my 2015 Lincoln MKC I was having trouble with battery going dead almost from new. There was a lot of talk about the key fob always communicating with the car when in close proximity. I researched this mainly through a site Forscan.org and found how I could turn the BMS off with Forscan and this seems to have corrected the battery problem.
It's interesting that you had a new key fob programmed and the tech was having trouble with "the computer" your - tune and he may have reset the BMS with their equipment which is not advisable to do unless you are replacing the car battery and then to reset it to the proper type of battery. Who knows what he did and it seems you suspect something on his part. In any event I would look at the site I suggested and search for BMS problems and you will find lots of discussions. Have a look here as well: https://docs.google.com/spreadsheets...o60/edit#gid=0
Good luck

 

Very interesting - I'll definitely dig into this some if I find it isn't the alternator.

That key fob part is especially intriguing. I wouldn't have given it a second thought if it weren't for the fact that they vaguely said it was "difficult to program because of something with the computer". The other thing that strikes me in the quick scan of your link is the 8-hour sleep time after battery charge or change, and the fact that this morning when I had the car running for a minute or 2 for the first time in over 8 hours from the original troubleshooting, the issues were no longer present. I'l have to run it for longer when I get home, but man it would be sweet if the problem corrected itself. Although as someone who troubleshoots electro-mechanical systems for a living, I'd give it an F on it's design with regard to error reporting for troubleshooting.

 

Look under battery on this site. https://docs.google.com/spreadsheets...o60/edit#gid=0 It gives all the battery codes you can input in Forscan. Near the bottom is how you can turn the battery management system off. I know this is an Explorer spreadsheet, but all the Ford vehicles have almost identical coding for their options. Up until 2015 all were Sync 2 and starting in 2016 Ford implemented Sync 3. Another thing I did was start keeping my FOB further from the attached garage and that seemed to help with the Lincoln battery.

 

Have you checked all of your main grounds to make sure none are loose,corroded or disconnected,since the issues aren't present with the engine off,but they are with the engine running?? IOW- a loose ground may not present itself with the engine off,but with it running and vibration being present,it may cause issues.

 

So my fingers are crossed that it was related to the 8-hour sleep time the BMS requires, because I took it for a 30 minute ride after work yesterday and had zero issues. Do to the intermittent nature of these types of electrical problems, I'm not writing it off as fixed yet, but I sure am hoping so. Gotta love a car that fixes itself, haha! I am still intrigued to see if I can dig more data up using Forscan when I get the adapter in, and see if I can confirm one way or the other. I appreciate the feedback from everyone to this point.

Thanks - This is great, I ordered the OBDII adapter they suggest and downloaded Forscan, very excited to use it.

Thanks - This is a good point and something I've been putting off. The car is immaculate underneath so I'd be bummed if this were an issue, but definitely not ruling it out.

 

Cars that fix themselves can also unfix themselves. Hopefully in your case, you've solved your problem once and for all.