[Tif5572]

Anyone ever have the issue of the computer for the engine and the computer for the transmission miscommunicate and the car go into limp mode?? Just happened to me today and was not fun! I went to pass someone leaving my town and the car just bogged down badly. After shutting it off for a few minutes and restarting it, it was fine but super weird!

 

[maydk65]

Multiple threads on this.

 

[Engineer]

This has happened on mine a few times. Nothing in the DTCs other than communication errors. Starts right back up. Has always happened after I come to a stop from modest speed, then turn left and start to accelerate, just a few minutes after a cold start, if it's going to happen. I've started carrying an OBDII reader in the car so I can always be ready. At least two of the times I had just filled up that day or the night before. So I started thinking this way:

1. Communications failures can be all kinds of things. While they can be hard failures, they can also just be overloaded data links from a lot happening at once. So I don't want to read too much into the communications failures without something else to back them up.
2. I started thinking about what else might make a car stall after driving 45 or so, stopping, turning left and accelerating. Hmmmmmm... Maybe moisture in the tank?

I know my car sat on the dealer lot for months. Check.
Stopping would cause some inertial movement of the fuel in the tank. Check.
Turning and accelerating? Same thing. Check.
Communications failures? Well I imagine if your injectors pull in water and the engine chokes there would be all kinds of messages across the CAN bus in a hurry. Check.

So even though they don't recommend it in the manual, I bought a bottle of fuel system cleaner and put it in and filled the rest of the way with 93. Haven't had a problem since. Did it fix it? Who knows.

 

[Tif5572]

This has happened on mine a few times. Nothing in the DTCs other than communication errors. Starts right back up. Has always happened after I come to a stop from modest speed, then turn left and start to accelerate, just a few minutes after a cold start, if it's going to happen. I've started carrying an OBDII reader in the car so I can always be ready. At least two of the times I had just filled up that day or the night before. So I started thinking this way:

1. Communications failures can be all kinds of things. While they can be hard failures, they can also just be overloaded data links from a lot happening at once. So I don't want to read too much into the communications failures without something else to back them up.
2. I started thinking about what else might make a car stall after driving 45 or so, stopping, turning left and accelerating. Hmmmmmm... Maybe moisture in the tank?

I know my car sat on the dealer lot for months. Check.
Stopping would cause some inertial movement of the fuel in the tank. Check.
Turning and accelerating? Same thing. Check.
Communications failures? Well I imagine if your injectors pull in water and the engine chokes there would be all kinds of messages across the CAN bus in a hurry. Check.

So even though they don't recommend it in the manual, I bought a bottle of fuel system cleaner and put it in and filled the rest of the way with 93. Haven't had a problem since. Did it fix it? Who knows.

Yeah I don’t have a clue as to why mine happened. I always let the car warm up before I go anywhere, even in summer. It happened to me when I was going 25 through town and then I went to hammer on it to pass someone (because they were still doing 25 after it changed to 55😅). I also had the AC cranked but 🤷🏼‍♀️🤷🏼‍♀️ My car was a lease then I bought it right after the dealer got it from auction because he went to auction looking for AWD fusions for me. So
it didn’t sit like yours but who knows. Electrical is so hard to figure out on cars lol

 

[Engineer]

@Tif5572 That is one thing I've noticed though, is just like you, when it's happened on mine it's been when I punch it. And I'm not moving fast either. So like turning left, I'd get through the turn them it would stall. So basically moving probably close to 25 I'm guessing at the stall point. Not sure if that has anything to do with it or not. Part of the problem is it's so hard to reproduce, and it's so intermittent, that it's really tough to diagnose. I'm just not sure whether the electrical is the cause, or is just secondary. In other words, with all those CAN bus errors, it seems like people are thinking the communications failure is the cause. I'm just saying I think the CAN bus would see a flood of activity if the engine stalls in operation like that, and I imagine data link saturation would cause a rash of communication failures. So I'm not convinced those are the cause. They might be, but I don't see anything so far that tells me that.