My PowerBoost is essentially dead

[Josh35]

Wow didn’t know my thread was still an active discussion. Just a refresher, ultimately they replaced my entire wiring harness. 1 year later the truck is working perfectly since .

I should include that the truck worked perfectly fine during the cold winter also (that’s the only time when my issues occurred)

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[DerekB]

It would be interesting if someone could make a poll to see what percent of us have had a no start condition with the stop safely now. Parameters could be mileage it occurred, what the solutions were found to be, and if the truck has had any issues since the repair. I saw a similar poll on different issue. If someone more savvy than me could make a poll like that it would be great for all of us to know the statistics. I’d also like to know more about the people who have had buybacks or lemon laws and generally speaking what Ford or the dealers have done to make it right.
In my case so far my dealer filed an extension for me to have a longer rental. I’ve heard other guys say they couldn’t get a loaner or some guys saying they only approved a rental short term. In my case I’ve had a rental for almost a month and it’s supposedly being paid for. Anyway some of you might have more ideas for other parameters. If I knew how to do this I would do it.
Thanks.

 

[Joekr5]

With (apparently) little else to do this evening, I just read this 16 page thread. Between Josh35 and devern I feel like I just watched a mini-series! Our first hero overcame his dire situation and rode off into the sunset (or blizzard...he's Canadian) while our second hero will have to wait for the season 2 premier before we know his fate.

Please know I only poke fun in jest. There are many folks in this thread going through expensive & frustrating ordeals. But still, I feel like I just came out of the theater after a Marvel movie!

 

[GinoM3078]

Well I promised to keep y’all updated. After a week at the dealer, still no cause for the gear shift to move to park by itself. On to week #2. To be continued.

Just given update, bad fuse box. 4-5 days on new one yo replace.

 

[devern]

So that's 2 counts of electrical components then. My saga continues. Crawled under the truck today, trying to inspect anywhere the dealer has serviced for anything out of place. I don't know if there is typically lubricant flung everywhere where the electric drive unit connects to the driveshaft or if it's just me...

The work order where they completed 21S56 (sagging underbody shield) was completed, and I noticed it states they had to remove the inverter to install the rivets. Didn't look out of place, but I wonder...

 

[Snakebitten]

The electric drive is on the opposite end of the transmission from the drive shaft. It's tucked in right behind the torque converter.

 

[devern]

Hmm. So I decided to try again, since it's a nice warm day. Truck has not been driven in a few days and it won't start right now. I think that discounts my theory about heat soaking being required to replicate the problem. A quick scan and visual inspection revealed new information. There was a ton of condensation on the aux 12V battery!

It was very hot and humid in the cab of the truck, as has been our experience when this happens... but for an AGM battery to "sweat"? No signs of moisture ingress, no wet fabric around the battery at all...

 

[Snakebitten]

So what are you going to try?

Just curious

 

[devern]

Well, first I need to evaluate the reasons why an AGM battery could sweat, and then determine if any of those reasons could be cause for concern (overheating causing leakage as gas comes to mind). That's only reasonable if the gas is expelled at a much higher temperature than the battery enclosure, hence condensation. The battery compartment and aux battery were both cool to the touch, despite the extreme heat of the inside of the cab, so it's unlikely that hot weather is causing the condensation directly.

I expect the aux battery is quite likely toast, just from initial googling. I guess I circle back to my post from a week ago. I should try the cheap experiment of replacing the aux 12V battery. Maybe my dealer will have some inside knowledge about this and offer to do it for me haha

 

[Snakebitten]

I was wondering if you were going to disconnect both batteries momentarily to see if it "reset" whatever.

 

[devern]

I was wondering if you were going to disconnect both batteries momentarily to see if it "reset" whatever.

I've been hesitant to do that because I have read that it wipes out any stored preferences, but I mean... at this point, why not?

 

[devern]

Well, that slightly altered the behaviour, had both batteries disconnected for a good 5 minutes or so. I'm now getting incessant chiming with the vehicle off and the door open, like it thinks the vehicle is in motion while the door open. The light beside "P" on the gear selector sometime flashes quickly now too (maybe this was already happening, but I didn't notice). I would guess a faulting module is locking the drivetrain (I've read ABS can do this if the TCM gets invalid data from it).

Also, it looks like the aux 12V battery has a coolant line attached to it underneath the red terminal. Or maybe that's a vent line?

 

[devern]

So two other owners with similar problems many moons ago have had their problem resolved by replacing the aux battery isolator. I found an old post that had detail on how the aux battery is used by the PowerBoost.

Maybe this supposed 12V drop we've been chasing is because the aux battery isolator is either not receiving the PWM signal from the PCM, or is not closing as directed, preventing its additional 12V supply from powering the modules. Or maybe the condensation is somehow causing a short, or interfering with normal operation somehow.

Either way, the next time the truck starts, I wonder if I can force it into this condition by disconnecting the aux battery isolator.

 

[devern]

Ran again in the evening yesterday after cooling off. Disconnecting the aux battery isolator doesn't result in a no start condition. Although, I am pretty confident the vehicle enters this state well before attempting to start the vehicle. There are a few tells that it's not going to start as you approach the vehicle with the key fob. The most noticeable is that the driver's seat does not move when the door is unlocked. Typically it would slide back to ease entry, then position to the stored setting for the respective fob.

The more I think about it... the aux battery isolator communicates with the PCM over a LIN network, meaning its communications would also contain a checksum. So it's unlikely that there would be invalid data without storing a fault code.

 

[devern]

I just re-read that and the aux battery isolator is in the engine bay; it is apparently not the hall effect sensor on the neutral wire near the aux battery.

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