Repeat “Electrical System Drain” alert after 12 V battery + full module re-flash

[UK Bills Backer]

I could use the community brain-trust (and, if any Ford Master Techs are lurking, your insight) on a stubborn low-voltage fault in my 2023 Lightning Lariat.

(Hi - I'm Nick, a new Lightning owner and new to the forums here. Thank you all for being such a great resource)

Quick specs

• Build & trim: 2023 Lariat, extended-range pack, SRW

• Current kms: ~ 15,000

• In-service date (used purchase): 25 Jun 2025 (hit the road with first owner January 2023)

• Region: Ontario, Canada (so Ford of Canada warranty rules & CAMVAP apply)

• Mods: Bone-stock — no aftermarket electronics, dash cams, etc.

The problem

• 13 Jul 2025 – “Electrical System Drain — Service Required” popped up while parked at \~90 % SOC after a day in 32 °C heat.

• 28 Jun 2025 – Same warning triggered → dealer replaced 12 V battery (BAGM-H3) and flashed every control module (FHCM, BECM, BCM, PCM, DCDC, APIM, etc.). Drove fine for nine days.

• History: CARFAX shows six service visits in 18 months (<14 k km) — several list “electrical system checked.” Dealer that sold me the truck did not provide this report until I asked post-purchase.

• Usage: Plugged in every night to 40-amp ChargePoint Home Flex. No unusual 12 V accessories.

• Symptom pattern: Both alerts came after the truck sat hot for a few hours (once in the sun, once after a highway run). No deep-sleep issues noted in cooler temps.

What’s been done

On first issue (three days after owning the vehicle), I took it to the dealer I purchased from. They did:

1. New 12 V battery and battery monitoring reset.
2. Module updates per TSB 24-2103 and related SSMs (per invoice) - basically a full refresh of all modules. The list was SUPER long.
3. Basic parasitic-draw check. Dealer says “couldn’t replicate.”

Questions for the hive mind

1. Known culprits? Hearing rumours about the Body Control Module or gateway module not sleeping. Anyone replaced these and solved the drain?
2. DC-DC converter failures — how often are Lightnings seeing that part go bad? Any TSBs/SSMs I can cite?
3. Software vs hardware? At what point did your dealer move past reflashes and start swapping modules or harnesses?
4. Canadian owners: Experiences with CAMVAP or OMVIC when electrical gremlins persist?
5. Temp-related triggers: Anyone link this fault to hot-soak conditions? (Ontario hit 32 °C / 90 °F yesterday. And hit over 38 °C / 100 °F the first time this error cam up for me.)

Why I care (and why time matters)

Two family road-trips (Montreal Wednesday; Nashville Sun.) are now at risk. I’ve already had one summer vacation scrambled by this. Hoping not to make it three.

What I’m doing next

• Demand full OASIS + prior ROs from dealer.

• Get dealer to do overnight draw test; verify new battery coded to BECM.

• Opened Ford CRC case; will file CAMVAP if not fixed on this round.

• Buying a lithium jump pack to store in the frunk just in case.

Any insight, success stories, part numbers, or escalation tips are hugely appreciated. Thanks in advance!

(I’ll report back so the next Lightning owner can benefit.)

PS - happy to share last three of the VIN if any insiders can peek at history.

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[TaxmanHog]

Though you don't have the same symptoms, I wonder if your BECM is also going on the fritz ?

https://www.f150lightningforum.com/...orking-update-truck-is-dead.29250/post-545137

 

[Maquis]

Check that 23B70 has been carried out on your truck. It involves the 12V battery sensor.

 

[Adventureboy]

There are a number of threads on the forum on this topic. Low SOC on the LVB can be caused by a number of things. Short drives or driveway shuffles are particularly hard on it since they light up all of the modules for about 1/2 hour and after 2-3 shuffles, I'll get this message. Also, not driving the truck for a while, but walking by it lights up the approach modules, so make sure your keys/phone are far enough away to keep the truck from lighting up. Perhaps turn your approach lights off for a while to see if it still helps.
The truck will charge the LVB from the HVB when it gives you this message, so it is unlikely you will need the jump box, but good to have anyway.

Also, when plugged in, the truck will only charge the LVB while the HVB is charging. It will then start discharging the LVB even if the truck is plugged in. Not the best scenario but good to know.

 

[evtrapper]

We just need to engineer a trickle charger for that 12v that doesn't involve opening the frunk. Even better if it involves a solar panel & is portable.

 

[Adventureboy]

We just need to engineer a trickle charger for that 12v that doesn't involve opening the frunk. Even better if it involves a solar panel & is portable.

I installed a Noco 5 amp charger on the back of the 12v access hatch at the back of the Frunk and installed a 120 volt RV power port just behind the bumper in the air scoop. It's really easy to plug in when needed. It shouldn't be needed, but it is. If I have to shuffle the truck a few times between drives, or won't be driving for a few days, I just plug it in.

 

[UK Bills Backer]

Check that 23B70 has been carried out on your truck. It involves the 12V battery sensor.

Confirmed - complete.

The latest on by truck is this: Dealer has been doing draw tests. No drain identified. They have identified a persistent fault code pointing at the body control module. Based on the history of 4 12v battery replacements in 3 years, they are trying to go a bit deeper before they just chuck a new BCM in it.

 

[Adventureboy]

Confirmed - complete.

The latest on by truck is this: Dealer has been doing draw tests. No drain identified. They have identified a persistent fault code pointing at the body control module. Based on the history of 4 12v battery replacements in 3 years, they are trying to go a bit deeper before they just chuck a new BCM in it.

This may be good news. A persistent BCM fault would definitely cause battery issues and may have been the problem since new. BTW, I have the same truck in service in Ontario Jan. 2023. I'm on my 3rd 12v battery but mine is caused by constant short drives and driveway shuffling. An external battery monitor was helpful for me to diagnose my driving pattern as the problem.

 

[UK Bills Backer]

This may be good news. A persistent BCM fault would definitely cause battery issues and may have been the problem since new. BTW, I have the same truck in service in Ontario Jan. 2023. I'm on my 3rd 12v battery but mine is caused by constant short drives and driveway shuffling. An external battery monitor was helpful for me to diagnose my driving pattern as the problem.

I suspect that the BCM code that they are seeing now HAS been there all along. I pressed my dealer service leader to ask Ford to reveal the history of faults logged (presumably Ford can see further back than 3 months). If the BCM fault code pops up all the time I feel like the module itself is the problem and I would feel pretty confident if they replace that entirely and send me back out on the road.

I have time, because we're off to France for a couple of weeks next week. But boy is this every frustrating to have spent CAD 70k on a new vehicle to only drive it for 12 total days in 2 months of ownership!

 

[Adventureboy]

I hope replacing the module solves the issue for you. I've had good luck with mine. Onboard charger had to be replaced and lost only 3 days on that - The part took 2 weeks, but I could still drive on DCFC until it arrived. Otherwise, it has been very reliable.
I installed this:
https://www.amazon.ca/ANCEL-BM200-B...8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

It was instrumental in determining the patterns leading to the 12v battery messages.

 

[epluribusunom]

Was it not charging your 12v when you drove?

 

[epluribusunom]

I’m having issues with parasitic draw, battery is 100% when I get home but the next day it’s at less than 50%

 

[Adventureboy]

I’m having issues with parasitic draw, battery is 100% when I get home but the next day it’s at less than 50%

This happened to me when I installed a dashcam that remained active when off. I had to disable that feature and only operate it while driving. The difference was 30 vs 300 milliamphours standby draw for the whole truck.

 

[epluribusunom]

I wish mine were that easy.

I have nothing plugged in to the truck. I even disabled PAAK. Still continues to have parasitic draw. I'm thinking it's a faulty module or something that wont go to sleep. OBD Scanner shows around 5-6amp draw when everything is completely off.

If I go back to my truck after a few hours it disables the cabin lights when I open the doors.

Not sure what the deal is.

 

[Maquis]

I saw a video online where a shop used a thermal camera pointed at the fuse box to find the circuit causing parasitic draw. They left the car off for a few hours to let everything stabilize. The camera easily identified the warm fuse.

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