Mustang Electrical Gremlins??

Question

Long time Scotty follower, first time poster! I have a "gremlin" in my Mustang. Let me explain (& please follow along, it's detailed so you know what I see & we're both on the same page)

16 Mustang, V6 base model, 6 speed auto. Nothing fancy. Bought it new in '16. No issues up until about 2 weeks ago. I replaced the factory original battery because it was 5 years old & the car cranked slower than normal a few times & the right tail light didn't always flash when I grab the door handle to unlock & open the door. The left always did. I thought "low voltage/current") Following me?? After replacing the battery, both flash every time & now cranks like normal. Maybe that fixed those issues? I hope so. Info cluster shows 14.4 charging, while the sitting voltage is 11.7 (ignition on, not running) with brand new battery, same as before swapping them. Those readings are NOT with a multimeter or a load tester, just what's in the info cluster. Now, here's the heart of my problem...yes another problem I can't solve!

The power ports under the climate controls & in the center console NOW shut off when I open the door, instead of staying energized for about an hour after I get out. I have a dashcam plugged into the 12 volt port under the climate controls. I need that cam powered on when I take short trips & need it to record what's happening in the parking lot. About 2 years ago, I had a hit & run on my car while getting groceries, the dashcam saved the day. Police report filed & their insurance contacted & paid out. (you see why I need the dashcam!)

Here's the weird part: both power ports WILL COME ON when I tap the power on the radio with the ignition off. They also shut off when I power down the radio. Both power ports also stay on after I drive, park & shut off ignition, BUT...lose 12 volt power as soon as I open the door to get out. The radio does too but I understand that part..all about keeping it available because of bluetooth. I hope this is making sense. Before this "gremlin" started. I could be in the car & parked, I have the radio on or off, & the power ports were still active because the dashcam would always be on, even with the doors open. I don't need the power always on (24/7) because I have a removable cam so I take it in at night, or when I know I'll be gone for more than an hour.

So...does the car need to re-learn correct voltages before it'll allow the power ports to stay active for an hour after ignition shut off & door open, or is there something simpler that I'm missing? I know the system reset when the battery was changed & had to re-learn fuel trims, ratios & everything else, but the power port issue happened shortly before the battery swap. Mechanic didn't have a memory saver, it seems to have re-learned trims & ratios in the past 4 days. Everything but the power ports problem. Fuses to check, relays to tap on...help me out here. I didn't have the old battery load tested because a slow crank can tell me weak battery, & I didn't want to have the "click of death" at the most inopportune time!

Thanks!
Scotty (yes, that's my real name!)

Dion · Answer

Does this Stang have some kind of custom setup options at all. Most GM vehicles have a setup where you can have the horn honk -off/on when the fob is pressed..and or lights come on for XXX minutes....You choose duration etc. Does the Ford have that? I am sure it has...On the GM sometimes those custom setting get reset from your custom setting before when the battery gets disconnected. Not suppose to but does.

Sweet16Mustang · Answer

It does have user settings through the information cluster...lights off time, courtesy wipe for the wipers, remote start duration, MyKey setup, track options & many others. But I do not see any option for the power ports. Since it seems to be (somehow) tied into the radio, I looked through the radio menu's but didn't see anything related to my issue. Sync 1 (the 4 inch screen) I forgot to mention that.

As soon as I got the car back from the mechanic, it's the first I did was to get into the user settings to change everything back, but everything was where I left it...nothing changed! Even the TPMS took about 5 minutes to re-learn pressure & physical position. Everything is back to normal BUT the power ports. As I said, it started this right before I changed the battery, thinking it was low voltage/current being 5 years old.

Sweet16Mustang · Answer

Well, folks...I've found the answer I'm looking for elsewhere, so here's the update. I've talked to people who know today's cars & they say:

BMS. Battery Management System. All 2011 & up Fords have it. An old battery going out trips the BMS (but never went into low power mode), cutting off power to accessories (the 12 volt power ports & that one tail light) when the car shuts off to save the battery from draining & prevent non-starting (a failsafe). The mechanic didn't reset it in the BCM with a scan tool (it only took 15 minutes to change it) & I can't really reset it myself right now. I CAN, however, reset the BMS by disconnecting the negative cable for 8 hours then reconnecting it. That'll have to wait until the rain stops! Putting in a NEW battery doesn't automatically reset the system, as the BMS thinks I still have an old aging battery in there so accessories won't stay on after the doors open, OR change the current/voltage from the alternator for a new battery. It's a "dumb" system, not smart enough to see a different voltage from a new battery, hence, resetting itself.

Simple, right??