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

[epluribusunom]

That is good info I’ll have to look into that. Thank you!

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[Adventureboy]

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.

OBD2 dongle will keep modules on while poling them. This will cause significantly higher than normal draw since it won't shut down the modules normally and you won't get a true standby reading. If you have an OBD2 scanner, there is a parameter called Quiescent Ave. This shows the average milliampere draw from the 12v battery while the truck is in standby after the modules shut down. It should be in the 30mA-50mA range for normal vehicles.

 

[epluribusunom]

Mine was at 72ma this morning when I checked the Quiescent Average

 

[Adventureboy]

Mine was at 72ma this morning when I checked the Quiescent Average

72ma would be about 5% SOC of a healthy 12v battery in a 24-hour period, so you should be able to go more than a week without battery messages if the truck is shutting down and staying in standby mode properly.
The other common issue is if the truck keeps getting woken up by keys, PAAK, door openings, Fordpass events, driveway shuffles, short drives etc., then the modules light up again. This can drain the 12v battery pretty quickly.
The OP may have a problem with a module that intermittently errors and doesn't shut down properly. Check your fault history with your OBD2.

 

[epluribusunom]

72ma would be about 5% SOC of a healthy 12v battery in a 24-hour period, so you should be able to go more than a week without battery messages if the truck is shutting down and staying in standby mode properly.
The other common issue is if the truck keeps getting woken up by keys, PAAK, door openings, Fordpass events, driveway shuffles, short drives etc., then the modules light up again. This can drain the 12v battery pretty quickly.
The OP may have a problem with a module that intermittently errors and doesn't shut down properly. Check your fault history with your OBD2.

It drains so fast though, certainly not 5%. And I bought a brand new battery (trying to fix the electrical drain warnings) directly from Ford. I'll have to figure out how to check the fault history, but that is good info thank you.

 

[lister coggs]

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.

Curious what the outcome was for this? I seem to be having the exact same issue. Dealer thinks it's the BCM and suggesting replacement, I'm out of warranty so hesitant on quickly accepting their assessment.

 

[UK Bills Backer]

So we think two issues were happening in my case. 1. Corrosion on the frunk button that wasn’t properly sealed causing the light to stay on. 2. A firewall gasket that didn’t completely get sealed from factory causing water ingress to the BCM which fried it intermittently.
Both were replaced and everything sealed and now everything works like a charm.

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