Hybrid battery drain issue / ACCM update (as of 11/8/25) -- Latest info from a tech's perspective

[Darryl]

We've performed the ACCM update on 4 Mavericks for battery drain. We've had success on 3 out of 4. Trust me. It's frustrating for US also.

On this one vehicle, it MIGHT drain overnight. And it MIGHT sit 2 weeks with no drain. I have performed a drain test. And it was clearly excessive. But it was quitting time. So when I fully charged the battery the next day and retested, the drain was 0.01A which is well within the acceptable 0.05A specified upper limit. Ford hotline escalated the report to the next level engineering team. Two days later they suggested disconnecting the Air conditioning control module (ACCM) and repeating the test during a high drain episode. Their conclusion was that in SOME cases the software update did not work. But they seem to think that the ACCM is still the source. Their advice was to release the vehicle to the customer. And they would be inform us when they had a permanent solution. And they are still working on a solution that will work for ALL cases.

That explains why the solution continues to be a SSM (special service message) because if a solution works in ALL cases, they usually upgrade it to a TSB (TECHNICAL SUPPORT BULLETIN).

What's the difference? From the technicians perspective , an SSM is a suggested repair. But we can try our own solution. But a TSB is something that REQUIRES us to attempt before doing something else. Otherwise they won't pay us.

So it seems that Ford was aware it would not fix every problem. But they were confident enough that it would fix a good number of them.

Sponsored

 

[skinnyboy]

Super appreciate you taking the time to post this!

Cheers.

 

[Darryl]

Super appreciate you taking the time to post this!

Cheers.

You're welcome

 

[Deb from MN]

Thank you for the info, it is truly the only thing about my truck that I dislike! VERY FRUSTRATING! I was told to just keep it hooked up to a charger, which I am not sure how to do, reg battery or hybrid battery. Bandaid fix at the very least.

 

[JohnCondren1933]

How long does it have to sit unused for the excessive drain to happen?

Ive never gone more than 3 days between uses, how do we know it happens does the Mav just refuse to start?

 

[CurtisB]

We've performed the ACCM update on 4 Mavericks for battery drain. We've had success on 3 out of 4. Trust me. It's frustrating for US also.

On this one vehicle, it MIGHT drain overnight. And it MIGHT sit 2 weeks with no drain. I have performed a drain test. And it was clearly excessive. But it was quitting time. So when I fully charged the battery the next day and retested, the drain was 0.01A which is well within the acceptable 0.05A specified upper limit. Ford hotline escalated the report to the next level engineering team. Two days later they suggested disconnecting the Air conditioning control module (ACCM) and repeating the test during a high drain episode. Their conclusion was that in SOME cases the software update did not work. But they seem to think that the ACCM is still the source. Their advice was to release the vehicle to the customer. And they would be inform us when they had a permanent solution. And they are still working on a solution that will work for ALL cases.

That explains why the solution continues to be a SSM (special service message) because if a solution works in ALL cases, they usually upgrade it to a TSB (TECHNICAL SUPPORT BULLETIN).

What's the difference? From the technicians perspective , an SSM is a suggested repair. But we can try our own solution. But a TSB is something that REQUIRES us to attempt before doing something else. Otherwise they won't pay us.

So it seems that Ford was aware it would not fix every problem. But they were confident enough that it would fix a good number of them.

This is really good to hear. I will say this. I can drive my truck non-stop from Orange County CA to Lake Havasu and back home, running the AC, and I will most likely get the "Sleep Mode" message the next morning. Thats just under 9 hours round trip driving.

If I drive the truck for weeks at a time, doing stop and go driving and I don't run the AC, ......no messages. The AC system has to have something to do with the drain.

 

[MarkLally]

We really appreciate this wright up. Even though most of will never have this problem, I think we have all heard about it and we all appreciate someone who is on the line explaining what you have been finding out there and telling us why the professionals do what the do.

 

[icegradner]

I sure hope Ford makes it a recall in the end, not just a TSB, so owners out of warranty aren't stuck paying diagnostic fees to fix this.

 

[Dad]

Thank you for keeping everyone informed. This has been a nagging problem since the Maverick's debut. Appreciate your vigilance.

 

[Propane Burning Man]

Thank you for the info, it is truly the only thing about my truck that I dislike! VERY FRUSTRATING! I was told to just keep it hooked up to a charger, which I am not sure how to do, reg battery or hybrid battery. Bandaid fix at the very least.

The small regular 12-volt battery is the one. Pop your hood and look for a small red plastic cover with a + sign on it. It is located in the center driver side area. Pop the cover off. Hook your + battery charger clamp to that lug. In the rear corner driver side area under the hood, you will see a negative lug sticking up that is screwed into the "chassis", it is aluminum in color. Hook your negative clamp on that lug. Yes, this is an inconvenience, about 5 minutes to hook up and then unhook. Nobody is enjoying this issue. However, if your battery is in a low state of charge your dome lights don't come on and your battery life will be shortened. That is a much bigger inconvenience. And more expensive. In my case I need to hook up the charger about every 10 days, when the dome lights fail to come on. Hope this helps.

 

[HeyBales]

Great info for those getting hit with that issue - especially as season of auto-AC use might be happening - so not turning AC on manually or by selecting temp, but just the higher humidity with cooler temps.

Question for my truck.
New battery in July.
Started at Ford special SOC of 85% fulling charged - 12.7 V resting.
6 days at this pic, now 80% SOC - at least it was willing to throw 5A at it!
Took pic because it just went to 1 Ah of cumulative charge (or perhaps 0.5 and it rounded up), before discharge reaching the same figure.
So it should have been on the winning side of keeping the SOC at 85% fully charged. More charge than discharge Ah's - according to it's logging.
So it thought it was - but obviously wasn't or the battery wouldn't have decreased in charge.

Anyway - it's the Battery Quiescent Current PID below - during prior sleep mode, when it should be 25-50 mA.
Below is 69 mA, rarely is it below 50. Gotten some 20's, saw an 18 after 2 days of sitting - so I think it's average not max reading.

Would the ACCM issue cause a drain during sleep mode? (75 min after turnoff)
And would it be mere milliamps if it happens?
Ya - still micro-drain, so not exactly an intermittent battery drain causing an issue.
I still haven't had the ACCM update done since I haven't had an issue.
I'm not using AC manually, but I can tell it's on sometimes for the humidity.

 

[Darryl]

How long does it have to sit unused for the excessive drain to happen?

Ive never gone more than 3 days between uses, how do we know it happens does the Mav just refuse to start?

For most vehicles it never happens. But for those that have the problem, it seldom shows up if the truck is driven daily once the battery is fully charged.. if a battery is a good battery and fully charged, it will usually take 2 or more days before it dies enough to where it won't start. Again, most hybrids do not have problems. But for those that do have the problem, it can be persistent and frustrating

 

[Darryl]

I sure hope Ford makes it a recall in the end, not just a TSB, so owners out of warranty aren't stuck paying diagnostic fees to fix this.

Me too. it would be good public relations. And would simply be the right thing. Hopefully, it will still be something they can correct with software or a minor part

 

[Darryl]

Thank you for the info, it is truly the only thing about my truck that I dislike! VERY FRUSTRATING! I was told to just keep it hooked up to a charger, which I am not sure how to do, reg battery or hybrid battery. Bandaid fix at the very least.

The 12 v battery, you can access the battery itself under the rear seat. But that's not necessary because they have a connection under the hood on the driver's side where you can connect a trickle charger or jumper cables if necessary. The problem can be sometimes mitigated by starting it daily

 

[Darryl]

Great info for those getting hit with that issue - especially as season of auto-AC use might be happening - so not turning AC on manually or by selecting temp, but just the higher humidity with cooler temps.

Question for my truck.
New battery in July.
Started at Ford special SOC of 85% fulling charged - 12.7 V resting.
6 days at this pic, now 80% SOC - at least it was willing to throw 5A at it!
Took pic because it just went to 1 Ah of cumulative charge (or perhaps 0.5 and it rounded up), before discharge reaching the same figure.
So it should have been on the winning side of keeping the SOC at 85% fully charged. More charge than discharge Ah's - according to it's logging.
So it thought it was - but obviously wasn't or the battery wouldn't have decreased in charge.

Anyway - it's the Battery Quiescent Current PID below - during prior sleep mode, when it should be 25-50 mA.
Below is 69 mA, rarely is it below 50. Gotten some 20's, saw an 18 after 2 days of sitting - so I think it's average not max reading.

Would the ACCM issue cause a drain during sleep mode? (75 min after turnoff)
And would it be mere milliamps if it happens?
Ya - still micro-drain, so not exactly an intermittent battery drain causing an issue.
I still haven't had the ACCM update done since I haven't had an issue.
I'm not using AC manually, but I can tell it's on sometimes for the humidity.

If you don't have an issue m there's no need to do anything. . The reason the battery drains is because something is not allowing a module to completely go to sleep. But even in sleep mode , which can take over a half hour for all modules to go to sleep, Ford allows up to a 0.05A parasitic current draw. I don't know if they set your battery monitor when they replaced your battery. Sometimes a tech will forget to do it. If they didn't, it could be giving an inaccurate reading. But as long as it doesn't drop below 80% you won't have any problems.

Sponsored