My 2018 f150 has experienced a periodic issue with the start stop feature (about 3 months). Its totally inconsistent. Sometimes it starts right up without hesitation and other times it’s sluggish during start, comes to a complete stop during cranking, then eventually starts. A couple of times, it wouldnt start at all and indicated shift to park and restart vehicle. I recently tried to use remote start and it began to crank and completely stopped before turning over. Im having the battery replaced this week even though it tested normal and hoping that will take care of the problem. Anyone know how this system works and or have dealt with and resolved this ?

 

My recommendation is to completely disable auto start/stop. This can be done by purchasing and hooking it up to a Windows laptop running https://forscan.org/home.html which you can use for free by registering for a Extended License Key 2 month trial. Hit up the https://www.f150forum.com/f118/forscan-software-enable-disable-features-your-truck-348987/ on this very forum, open the My 2015-2019 F150 as-built decoding https://docs.google.com/spreadsheets/d/1uDSQ1Z5a2Wt8-kjrSiVSlDFGFHnfeuhb3RTMVz95730and find the auto start/stop disable setting in the BCM at very top. Program it, apply and watch your truck make noises and sounds for a few seconds, and then never have to deal with this function ever again for the life of your vehicle until you decide to revert it back via the same method (and you can re-register for another free 2 month trial at any point in the future).

 

If you have been using the Auto-Stop-Start a lot over the years, than there is a good chance your starter motor is showing the early signs of failing. I'm not sure the benefits of A-S-S aren't offset by the increased wear and tear on the starter. I'm lucky, my truck doesn't have A-S-S.

 

From your description, I think something else is at fault.
1. It's not a stop start fault because the system is attempting to do auto start.
If the voltage was (not) up to the voltage monitored value and there is no hard fault code set in the system at that time, it would not even attempt to auto start.
2. Once the starter tries to draw that large amount of current, the circuit fault becomes present.
3. Manual cranking would also fail at times, under the conditions.
.
It may be the starter, it may be the cable connections at the Battery, it may be a poor ground connection at the battery ground to chassis lead or even at the bell housing area bolts loose etc.
Take a wider look at all this so you don't miss it.
Good luck.

 

Youre also disabling other features by using the forscan method. The auto s/s eliminator would probably be better if you want to get rid of it.

Or, just press the button every time you start your truck. It’s easier than putting on your seatbelt, and it’s free. I like to have the option of turning back on the auto s/s every so often at long traffic lights.

 

I do NOT think it is an issue with the auto s/s system. Because you have similar issues when trying to start with remote start, it indicates issues identified by 52merc and bluegrass posts above. Using the "auto s/s eliminator" would NOT help.

 

Thanks all