CAN Bus Disaster over a battery.

[Fordiesel69]

My 2018 F150 only had its auto start / stop work for maybe a month last year in 2024. Then it never worked (thank gawd). The engine always cranked over super fast, even in cold weather.

2 weeks ago I heard an audible change in the starter sound, where it sounded like a normal car, not ultra fast like it usually does. Not long after I would get intermittent "drive modes not available", or "Traction Control Disabled", and a weird electrical behavior like slow and uneven turn signals.

Upon a code scan there were communication issues, and also
U0200 - Lost Comm With Door Ctrl Module B
U0199 - Lost Comm With Door Ctrl Module A

Charging was good, starting was slower but still good. I had battery tested and it scored a B-. It floats at 12.4vdc, then if you turn headlamps on it drops to 11.98dvc.

After changing the battery for a new AGM and resetting the BMC, it now has resolved all issues. It auto starts / stops every time now which is annoying.

 

[bdcardinal]

It will stop doing the auto start stop once the battery reaches a certain level of state of charge. If you plug one of those 7 pin testers into your 7 pin trailer connector it will turn off the auto start stop.

 

[Rand]

What was the disaster? I was figuring you had to do a proxy realignment or similar.

 

[rijndael]

Upon a code scan there were communication issues, and also
U0200 - Lost Comm With Door Ctrl Module B
U0199 - Lost Comm With Door Ctrl Module A

Unrelated to your issue. Many Fords have these codes.

 

[JohnnyG]

That's the first sign that my battery is low in my MB, no start/stop. The second thing that happens if it gets low enough, is the sunroof opens on it's own!
8 hrs, with my NOCO 5 fixes things up.

 

[MNgopher]

Disaster? What disaster?

The truck gave you multiple warning signs your battery was on the way out. All the weird faults are the usual things that start happening, but the start stop not working is the first clue. You can access a screen that tells you why the truck is in the mode it is in. When it always says the vehicle is on for charging you have your first clue to monitor the battery health. Not abnormal for it to work that way now and then, but all the time is a clue.

If you have fordpass setup it would also be telling you that its disabling systems to protect the battery...

 

[JRay’07]

The high end NOCO chargers are compatible with these systems.

 

[Danno]

Click bait?

 

[KGMtech]

That's the first sign that my battery is low in my MB, no start/stop. The second thing that happens if it gets low enough, is the sunroof opens on it's own!
8 hrs, with my NOCO 5 fixes things up.

That sunroof issue would be horrible if you're hit with a rainstorm...in Florida !!

 

[CKN]

There are so many issues on the F150 that if you have an issue many,many have had it before. It's a known issue that the start/ stop not working points to a bad battery. What's the big deal?

 

[supton]

If the truck was so smart, why couldn't it just display a message on the dash that said "please charge the battery!"

I still don't get why so many components work poorly at low voltage. Yes I know they can have serious power draw, and have min voltage requirements--but the control bits ought to work down to low voltages and realize the problem, and not set incorrect codes.

 

[ElectroMechanoMan]

They work poorly because when the voltage the ECM uses for a logic 1 or 0 is not in spec, it doesn’t know how to interpret it. That also goes for 12V field inputs. They also have thresholds for on or off. All of this can cause weird problems to start happening. We see the same type of problems in industrial electronics, especially microprocessor based equipment.

 

[JohnnyG]

That sunroof issue would be horrible if you're hit with a rainstorm...in Florida !!

I know! And I've never had a chance to try this out, but there's "theoretically" rain sensors in the sunroof to close it. I had skylights in my last home with that feature, and it worked great. Maybe, in this case, it uses the windshield cameras for the sensor. I know it does for the automatic wipers.
The manual is huge and translated from German, so it's pretty difficult to tell which car has which feature.

 

[zzyzzx]

Forscan and a laptop can turn off stop/start permanently.