First post here and I'll try to sum up my issues pretty quick, hoping a lightbulb goes off in somebody's head or someone can at least point me in the right direction...

First off - 2015 XLT, 3.5L EcoBoost, bone stock

About 2-3 weeks ago I got in the truck to leave a friend's house and the brake light on the dash came on as soon as I started it, never had it on before, no obvious issues with the truck as a result of the light. It was a very rainy day so I was suspecting something got wet somewhere along the way.

Fast forward to last weekend and I go to start the truck Saturday morning and the battery is completely dead, can't even get the radio or lights on, the best I could do to see any hint of electricity was get the seat to move about an inch. I had just driven it the night before with no issues (Other than the brake light still being on), but it was another rainy night. Being in a rush to leave for an overnight trip we took my wife's car and I didn't have time to mess with it on Saturday.

After getting home Sunday and jumping it, I noticed my backup camera would no longer work (Worked fine when I last parked it before the dead battery), giving the "Rear view camera unavailable" message. Voltage was fine from the alternator, about 14.7v, and after letting the battery charge for about 40 minutes, it continued to start fine on its own. To the best f my knowledge, nothing was "left on" to have killed the battery Friday night, still a mystery. I did end up replacing the battery Monday just to be safe, it seemed to only want to stay around 12.3v after charging which isn't great, and at about 4 years old it wouldn't be unheard of for it be on its way out anyway.

To try and troubleshoot the brake light and camera issue I ran ForScan and got B1048:01 (Brake Fluid Level Switch: General Electrical Failure) and B115E:08 (Camera Module: Bus Signal/Message Failure). I wanted to try and track down the brake light first, but both seem to possibly come back to a potential wiring issue somewhere to the BCM. I thought I had the fluid level switch down to a bad sensor by following some youtube video of connecting the 2 pins to the sensor to see if the lights goes out, and it did, but already put a new one in to no avail. To fully troubleshoot, the shop manual wants me to Disconnect C2280F from the BCM and then check for voltage at the fluid level sensor. I'm having trouble figuring out which connector that actually is. In all of the 14k pages of the manual I got, it only shows a diagram for the connector itself and not where it actually plugs into the BCM itself or which of the identified "J" ports it uses. Anyone know an easy way to identify which connect it actually is?

Any other suggestions of simple things to check before I go step by step through the shop manual troubleshooting steps are welcomed. Not sure if these two are at all related, but just seems like it can't be a coincidence two weird electrical things happen on rainy days only a few weeks apart. And still unsure what happened to have killed the battery so badly in just 1 night. Camera is still a complete mystery as well, seeing as I used to backup into my parking spot perfect fine, and came back dead after jumping it back to life.

 

How old is your battery? It may be on the edge. Take it out and put a full charge on it then have it load tested ( I prefer NAPA for this). While you are there see what deals they have on new batteries.

 

The battery is now brand new, has good voltage and holding a charge fine. That was replaced on Monday.

 

Have you had the issues since?

 

 

Yes issues are still present, the battery appears to have done nothing to fix actually fix anything.

 

Have you gone through to see if there is anything obvious with the wiring? I think I would try to see if and where the current draw is that is running the battery down. This can be difficult. Ideally you would want a meter that can read current without breaking the loop. Another thing to try, I'm not sure if you can with Forscan as I'm just learning it now myself, is to see if anything is switched on that shouldn't be with the ignition off. Maybe one of the timers for the lights is staying on.
I think your problem is in the BCM, which you seem headed toward. I'm not so certain it's electrical as it could be logic. I know you replaced the battery but maybe disconnecting the negative to do another reset would help clear any faults. I've found a reboot sometimes is just PFM (Pure F$#&!n Magic).

 

need to ask do you have sunroof? Have you noticed water on or around the BCM after it rains?

 

What's strange is the battery doesn't seem to be getting any significant draw on it. It died that one time but since has been fine and doesn't drop any noticeable voltage overnight at all, that seemed to be a one-time thing.
No sunroof on it, and not any rain that I've noticed, but hadn't really been specifically checking prior. No signs of any water that I can see.

As for the wiring, I haven't really gone through much yet, didn't really know where to even start, hence trying to figure out that connector on the BCM to see if I could at least follow the troubleshooting steps in the shop manual for the fluid level sensor circuit.

Forgot to mention - I did try disconnecting the battery twice more just to see if "resetting" anything would make a difference, and it didn't.

 

Couple of things - charging system varies output voltage and current to match the needs of the vehicle while monitoring the condition of the battery so with a new/fresh battery it is possible for the output voltage to drop near 12.2VDC as it will only supply the minimum needed to keep the systems up. It's also fine to notice this value move while running dependent on other things turning on. I like to gage vehicle on voltage with the headlights on - just as a base line. If I'm really worried I do headlights, AC, radio.

Now - BCM - battery condition monitor. It also protects the battery for undervolting when it sees the conditions for pulling the voltage down. This is also part of the "battery saver" circuit system. IE if you shut down leave your interior lights on over enough time the BCM circuit will command a shut down regardless of the switches because the engine isn't on. What that doesn't fix is any Open circuits on sensors. your battery fluid level switch might have shorted open - causing a fault conditions in the computer and the system stayed active even though the vehicle was shut down. There are a number of reports of things like that pulling down the battery. Parking sensors that trip (the beeps) prior to shutdown have also causes a similar situation. Computer stays in active mode instead of standby.

I suspect, sight unseen, that this is the cause of your first issue. replacing that brake level switch should be easy or you might even get by with unplugging it and leaving the wires OPEN as I don't know if that is a resistive switch or just a simple open/close. Then, check your fuses for the other systems that act odd. It's more likely your camera bit popped a fuse when it jump started or at least look for that - I like to ring out fuses with a multimeter since I don't see though then very well. IE multi-meter on continuity or resistance - and look for 0.0 Ohms. (short run should have near 0 resistance)

without looking at the panel I don't recall if the camera system has it's own relay - but another factor is to swap similar relays to verify the failure follows the relay. another easy fix.