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Discussion Starter #1
My wife's vehicle is a 2015 Ford Fiesta SE sedan. She has a normal turn key (not a push button FOB) setup. And we have the original two keys that came with the vehicle. Starting about two months ago she has had intermittent issues with the car not starting (not even attempting to start) and the dash display stating "Key not Detected". It would do this with either key, over and over.

After enough time passes (15-20 minutes), the car starts normally and works great. But that's a long time to be sitting at a gas station or stranded in a parking lot.

So I immediately replaced the batteries for the door lock/unlock part of the keys. That really has nothing to do with solving the issue but it made my wife feel good. Case in point - you can take the battery completely out of the key, get in the car, start the car, drive the car, etc. The battery is only necessary for lock, unlock, alarm, trunk functions.

The issue still happened. So last month I looked at the car's battery. It was four years and 10 months old. I replaced the car battery thinking that would solve the issue. I figured the battery was probably about to die and thus caused some electrical oddity. We switched cars for two weeks and there were no issues. We did fine for a month - until yesterday.

Yesterday (3/19/19) my wife got stuck at a gas station for about a half hour until the car decided to start. She parked it in the garage at home. When I got to look at it later, it still would not start. This was the first time I ever witnessed the problem firsthand. Put the key in and everything is okay. Turn the key and NOTHING happens with the starter. The display reads "Key Not Detected". Turn the key around, use the other key, wiggle the key in the ignition... nothing. Thirty minutes later... car works great! Works great with both keys.

So now it is working great. Seems weird to take it to the dealer. It will probably work great for 30 or more days. I have looked and looked and looked in google and youtube. Most of what I find is stuff about the fancy fords that have a push button start. Please note this fiesta is a turn key start. There is not some weird recovery FOB thing in the center console, door or glove box. The remaining google links seem to believe that cell phone interference is the culprit. That sounds "hokey" to me.

Has anyone else experienced this issue? If so, what actually solves it?

My theories:
Anti-Theft System Fault - would like to just turn that off is possible. Not like anyone is going to want to steal this car.
Faulty Ignition Switch - not sure if that would yield the "key not detected" error or not.
Dirty Ignition Cylinder - I'm going to get some contact cleaner and work on that
Need New Keys - seems doubtful... but maybe?

Thoughts?
 

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How much warranty do you have? If you don't have an extended service plan, you may be SOL. TBH, I would have done the same as you - batteries. Other than that I am as handy as a screen door in a submarine.

Sorry.
 

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Discussion Starter #4
No warranty remaining. It was 4yrs / 48k. The fiesta currently has 53k miles. It is also currently working great. I am really not sure what a mechanic would even do. No issue is present. I hooked up my decoder - no codes.

Ran it for 30 minutes. Starts back up fine. It’s just that I am not sure if a month from now it will leave my wife at a gas station turning the key for a half hour again. I guess that’s the time to have someone look at it. However if they don’t get to the car right away it will work fine again.

Weird.
 

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I wonder if you having the keys re-matched at the dealer would help. If it's both keys, it's not likely that both chips would be be bad at the same time, so maybe a security connection error that's intermittent.
 

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Discussion Starter #6
Well it worked fine for a month and had the same issue yesterday. I feel that the problem is with the theft deterrent system. A reset gets it back to where both keys start the car fine. From what I can tell online it takes 100 engine cycles until the issue comes back and then about 10-15 minutes for it to clear.

It’s just weird knowing that roughly once per month your car isn’t going to start right. I am not quite sure what to do here. It’s working great now. I can guesstimate that around this time next month there will be an issue again. But it will be gone 10-15 minutes later. It seems doubtful that I will be able to get the car to the dealer and then have the issue come up while it is in their possession. So not sure what to do here. Thoughts?
 

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Only thing I can think of is run it to around 98 engine cycles and drop it off. Sorry not more helpful. :(

Tell them what it's doing and have them drive the car a few days in a row through a complete warming cycle. Could be with ForScan hooked up, they'll get some signal or indication what's wrong.

I can't figure why the theft deterrent system counts through those cycles and hiccups like that. Usually when there's an issue with them, the car just won't start at all. Is there a way to bypass the theft deterrent?
 

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Discussion Starter #8
It has happened three more times since my last post. The first two the car started fine within 20 minutes of the failure and then worked flawlessly for about a week.

This evening it left my wife stranded at her work. She tried for about 40 minutes before I got there to pick her up. I tried for maybe 15 with both keys to no avail. I will go back there tomorrow. If the car doesn’t start I will have it towed to the dealer. If it does start I will drive it there.

Since the problem is becoming more frequent and more severe, I no longer suspect the theft system. I think it is the ignition switch sensor. I suspect the dealership can and will replace the ignition switch and reprogram both keys. Maybe $400? Not sure but this needs to end.
 

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Discussion Starter #9
Car dropped off at a Ford Dealership today around noon. No word yet. Hoping for a fix while preparing for a “we see nothing wrong” with a bill.
 

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Discussion Starter #10
Dropped the car off this past Thursday. It stayed until Tuesday. The solution (at the time) was that one of the keys had a short in it. $340ish covered the diagnostics and a new key. I picked the car up Tuesday of this week.

I drove the car to work and back on Wednesday. Everything was good.
I drove the car to work and back on Thursday. Everything was good.
I drove the car to work on Friday. After work, KEY NOT DETECTED.

It only took five or so tries and roughly five minutes and the car started again. Sometimes it's this quick to work; however, it is usually a 20 minute wait... sometimes it's hours. So I drove the car back to the Ford dealer and it's there now.

So if anyone else has this problem it is probably NOT:
Key FOB batteries... in this car those don't matter for operation. It is NOT a push button start. The key FOB batteries allow the unlock, lock, alarm and trunk buttons to work. That's their function. For fun, I did put new batteries in both.
Car battery. I replaced that... no change.
Your keys.

My guess is it's an intermittent short in the ignition switch. I feel that it is mechanical because it has become significantly more frequent over the past six months. It used to be a once a month thing... now it's at least once per week. However, I'm a software analyst... not a vehicle mechanic.

If they can't fix it, I feel like I am going to need to trade the car in. I dislike not knowing if when you stop for gas if you car will (A) start right up, (B) start in five minutes or so, (C) start with a 20 minute wait or (D) you have to call for a ride home. It's left my wife stranded a few times.
 

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I'm not sure about how Ford ignition switches are, but in my past life with a string of VWs, helping others with VWs, being on forums with other VW owners, when their ignition switches go bad, all sorts of flaky things happen. Stalling, non-starts, etc. I had one that would just kill the car, and the car wouldn't restart until the switch/car cooled off.

Is the KEY NOT DETECTED a function of the key being in the switch? Meaning, is the car primarily looking for a physical key in the tumblers? Or is the security system looking for a "handshake" signal from the key? Is there an RFID in the key that is bad, or is there an RFID reader in the car that's bad?

Reason I'm asking about an RFID portion of the system is that if the key is otherwise properly unlocking the doors, arming the alarm, unlocking the trunk, etc., then the powered portion of the system would seem to be working. Maybe the passive part is hosed.
 

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Discussion Starter #12
Thank you for your reply. That makes good sense about the ignition switch. The problem is only at startup and only happens sometimes (about once a week now vs once a month when it started). As for the keys, Ford said one of the keys was bad and made us a new one. I was then driving the car with the new key. For about three days it worked and then it would not start. So unless the brand new key was bad, I do not think that was the problem.
 

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While I don't have first hand experience on the system that Ford uses, the system will use some form of an NFC/RFID setup.
This means that there is a sensor (either as part of the ignition switch or right next to it) that reads the 'chip' in the key. The chip in the key is programmed into the car's computer as a valid key to start and to run the car.
I know of some third party remote start systems that require a valid key to be place near the sensor to allow the remote to start the car.

With all of that said, my thought is that it is either a failing sensor or the wiring to the sensor.
I did try a quick google search without much answers. One person online had an issue where their cell phone cause this kind of problem when it was too close to the ignition switch.
Not sure if this helps or not.
Brian
 

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Discussion Starter #14
Thank you. I also saw several posts about cell phones and interference. It has happened with no cell phone, my wife’s phone and with my phone. I don’t think that is our problem.

What you are saying about a sensor of sorts recognizing the key - that’s what I think is wrong. However, I am no mechanic. But the concept makes sense to me. The car has been with Ford the past seven days. No news yet.
 

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Discussion Starter #15
Yes I agree that whatever sensor there is in the car that recognizes the key is probably the problem. I do not believe it is cell phone related as it has happened with no phone around. Thank you.
 
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