2013 Fiesta (automatic) randomly loses transmission engagement

[Rokhnal]

Edit: according to the dealership I'm using the wrong terminology here and i should be saying "loses engagement" rather than "loses power". Updated title & body.

2013 Ford Fiesta, under 80k miles. The engine randomly loses engagement at a stop or at very low speeds; I put my foot on the gas and get no power but the engine revs, as if the car were in neutral. The engine is still on and all electronics and everything else works. If I put the car in park, I can't shift out of park until I turn it off and the engine "recovers" (which it does...eventually). So far I've driven the car for up to 20 minutes at neighborhood speeds with no issues.

Replaced the battery (it was time anyway) which didn't fix the problem. Mechanic ran an EVAP smoke test and found no leaks (though there was an old code for an air leak)--since the problem only happens when the engine is hot/after driving a while I suggested letting it run for a few hours and checking again. Waiting to hear back from the mechanic if they could replicate the problem.

A friend also suggested the fuel pump and/or filter could be the issue.

Ford has a CSP out for a TCM replacement and I've confirmed with Ford that I'm eligible, but the dealership wants $180 to test it (which I'd be responsible for if it's not the TCM)

Anyone experienced this before?

 

[Handy Andy]

Although the TCM and transmission get a lot of the (well deserved due to design) bad rap - this may also mean a bad/weak battery and poor connections and or loose serpentine belt is making the alternator slip and not keep up well enough to keep the power the TCM needs to keep the transmission engaged.

The power problem is twofold, it can also affect steering so you'd notice a pulsing or bump bump bump while trying to turn corners when slowed down - means the battery, alternator and their electrical delivery is not keeping up with the demand. Which signals a bad alternator, battery, loose serpentine or TCM is on it's way out and needs service.

Check out the Ford Focus issues and you'll see similar - but the TCM and Battery power issues show up together - so fixing one might help clear up the other - but the battery usually loses in the battle - due to age and connectors corrode.

So the battery may be ok, but the power to the TCM the battery and alternator supply to it can cause part of this problem which everyone seems to blame on the TCM. It can be a connector issue from corrosion. Why? - this seems to be low-miles for this to show up and if you haven't driven it hard or abused it - the TCM and the actuators - replacing the actuators usually clears up this condition for a short time, but it will return which goes to the transmission - I'm telling you this because the dealership has to cover their butts and have all the other problems that can cause these conditions - settled and fixed first before they spend the big-$$$ on the upgrade replacement.

 

[Rokhnal]

Figured I'd update: it's now been to the mechanic 2 more times, the dealership once, and I'm about to take it back to the dealership tomorrow. The first of those 2 times at the mechanic they drove it around for half a tank of gas and couldn't replicate the issue. Second time they replaced some of the transmission solenoid (which actually produced slightly smoother shifting than I'm used to, but didn't fix the problem).

The dealership reprogrammed the TCM (after several hours of labor and another half a tank of gas trying to replicate the problem with no success). He said without the TCM throwing a code indicating it's the troublemaker he can't put in for the extended warranty to replace it and it's $1k+ if I do it out of pocket, so hopefully he can pull something.

I don't think it's the battery or battery connection, the battery was replaced at the first mechanic visit a few months ago. I'm also not getting any stuttering, pulsing, shaking, or any symptoms at all *except* the loss of engagement when it happens. It's literally just like the car slips into neutral when I let off the accelerator completely (and randomly). So frustrating...

 

[Rokhnal]

Update: it was the TCM after all! The dealership was finally able to pull a code and it indicated the TCM is failing, and thankfully that's covered by the extended warranty. Fingers crossed this will be a permanent fix!