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Old 29-01-2019   #1
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Key won’t turn in its slot

I insert / push the keyfob into its slot, but when I try to turn the keyfob to start the engine, the keyfob won’t move and I get a “check car protection system” message and “symbol / picture of a car and padlock” warning light.

I remove the keyfob from its slot, reinsert the keyfob again into its slot, turn the keyfob again and the engine starts.

So far, the car always starts second time.

This happens with both our two keyfobs.

The Croma has done 120,000 miles, I’ve had it since 33,000 miles and it is running better than ever.

The battery is 5 years and 50,000 miles old.

The alternator is 2 years and 22,000 miles old.

Your advice will be appreciated; we’re motoring in France and Belgium in the Croma in February.
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Old 29-01-2019   #2
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Re: Key won’t turn in its slot

No longer have my Croma but from memory you may wish to try this.

The Croma key fob insetion slot has a release mechanism. The is (as I recall) a slot the same size and profile as the key fob's emergency mechanical key.

Inserting this key blade into the slot will release the key lock mechanism. What happens after that I have no info or experience. Suggest you just try and see what happens.
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Old 29-01-2019   #3
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Re: Key won’t turn in its slot

Be gentle with it.

Recently saw one of these ignition switches in bits, quite complicated, with 5 microswitches.
As the key is inserted, it reads the chip. If OK, it will move the locking mechanism to allow the key to turn. This is a small electric motor, with a gear to a rack to move small plastic bits along a slide. The emergency release uses the key blade to manually push this to one side.
You can't take the switch to bits and just remove this interlock, as when it gets to the end of its travel, it operates another microswitch to power up auxiliaries.
A new switch is frighteningly expensive.

Most cars carry the immobiliser code in the engine ECU and the body computer. The Croma also carries it in the ignition switch and the steering lock release module. Buying a used switch will bring a wrong code with it. If you get the key as well, it will not agree with the other three modules.

Obviously if a new uncoded unit is purchased, the Fiat dealer can code it to the car and your key. No idea if they can, or will, recode a used item. We certainly could not see such a facility within MultiECUscan, so did not try, for fear of uncoding the car.

The one we had in bits had suffered a spillage of sugary drink. Well placed directly in front of the cupholder, ready to catch any spilled liquids, followed by a firm stop.
Two of the microswitches were dead as a result.
To effect a fix, microswitches were removed from a used switch unit, and soldered onto the original circuit board, which contains the code chip memory. Required good skills with a soldering iron.

If taking it to bits, be very careful. Do it indoors, preferably inside a box, so stray pieces cannot be lost.
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Old 30-01-2019   #4
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Re: Key won’t turn in its slot

Get the vacuum cleaner and the round brush that comes with it and give the key reader a carefull cleaning. If the key does not seat properly it will not operate properly. Note the rader is part of the CODE system so you can't just fit a used one.

Robert G8RPI.
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Old 31-01-2019   #5
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Re: Key won’t turn in its slot

Thank you for your prompt advice. The problem persists.

The area is clean and the keyfob does seat properly.

Sliding the “emergency metal insert / key” (removed from the keyfob) into the small slot that is below and to the right of the keyfob slot, then pushing down eventually releases the lock mechanism and resets the warning light. But the problem reoccurs, when trying to start the car, several hours later.

I hope to avoid the expense and hassle of buying a new switch unit, having it fitted and coded to the car and keyfobs.

I’m tempted to have a new battery fitted, hoping that a slightly stronger battery cures the problem.

The car still always starts after keyfob removal and inserting for the second time.
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Old 01-02-2019   #6
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Re: Key won’t turn in its slot

Does anyone know whether the fob has a battery that can be changed. Just in case the one that's in it doesn't have enough charge left in it the first time you try it?
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Old 01-02-2019   #7
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Re: Key won’t turn in its slot

Quote Originally Posted by BrianMcL View Post
Does anyone know whether the fob has a battery that can be changed. Just in case the one that's in it doesn't have enough charge left in it the first time you try it?
The battery in the fob is for the remote locking only. This is irrelevant to the starting of the car. As evidenced by the number of cars with a spare key that is not a remote.
As well as the remote locking component, there is also a passive transponder chip, like the one a vet might pop into your pet's neck - no batteries there. When the key is inserted, an aerial around the lock reads the chip. On the Croma, as the key is inserted, it pushes a microswitch that powers the aerial to read the chip. If it accepts the chip, it then powers the release to allow the key to turn. Tiny little motor with a rack to move the interlock sideways.
The microswitches are tiny, and don't like coffee spilled into them. Any liquid or I suppose too much dust may cause the problems the OP has. My guess is that the microswitch that is pushed as the key is inserted is not making a good contact until pushed a second time.
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Old 02-02-2019   #8
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Re: Key won’t turn in its slot

Quote Originally Posted by BrianMcL View Post
Does anyone know whether the fob has a battery that can be changed. Just in case the one that's in it doesn't have enough charge left in it the first time you try it?
As Portlnd Bill says it won't be the battery. As it happens with both keys it is unlikely to be the transponder chip. Almost certainly a microswitch or other TEG (key reader) failure. Options are
1/ Buy a new "Virgin" TEG and get it fitted and coded - High parts cost plus some labour
2/ Buy a used TEG, ECU, Body computer, steering lock and keys and fit them all -medium parts, cost high labour
3/ fix the TEG or get it fixed. Possible DIY depends on skill level.

I can't find anyone listing a repair or virginising service for the TEG.


Does this only happen in th cold? I found this thread about another issue
https://www.digital-kaos.co.uk/forum...159-TEG-reader

Where are you located? I'd be happy to look at it for you or even if you sent the TEG to me. (I'm an electronics engineer).

Robert G8RPI.
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Old 02-02-2019   #9
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Re: Key won’t turn in its slot

I would be thinking now of going to a local Radio Spares and purchasing some professional switch clean and lubrication spray fluid.

Remove the switch unit and then thoroughly spray (with tube attached) into the microswitches and any other electrical contact or moving part. Also do the same for any connecting cable connectors.

Just last week I fixed a dishwasher rotary program dial switch unit that was not registering the correct program cycle as demanded on the dial. Same for a tumble dryer.

Has to be worth a go especially as your problem is intermittent.
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Old 07-02-2019   #10
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Re: Key won’t turn in its slot

My mechanic removed the switch unit from the centre console and blew air through it.

But the problem is still there, and the car always starts second time.

Could the problem be with the steering lock release mechanism?

A Fiat dealer told me the switch unit is no longer available (and that when available it would have cost 374 pounds including VAT).
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Old 08-02-2019   #11
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Re: Key won’t turn in its slot

Quote Originally Posted by uksdsgl View Post
My mechanic removed the switch unit from the centre console and blew air through it.

But the problem is still there, and the car always starts second time.

Could the problem be with the steering lock release mechanism?

A Fiat dealer told me the switch unit is no longer available (and that when available it would have cost 374 pounds including VAT).
Put the key in as quietly as possible and listen for the steering lock unlocking. However, I would not expect it to unlock unless the 'key in' microswitch actuates, and the key unit accepts the key. So whatever result you get is probably inconclusive.

If the microswitch is not making proper contact, blowing air through will do nothing. Contact cleaner might, but really, having seen the inside of these switches, only way to really tell is to dismantle it. The insides look complicated, but if dismantled carefully most bits will stay in place. A few dobs of correcting fluid may help.

I have taken the text from Fiat ePER which explains the operation of the switch. It is a Word document. If you cannot read it, squeak and I will try to convert it to pdf or an odt.
I have added my own diagram at the bottom that shows which microswitch is which on the circuit board.
Attached Files
File Type: doc Croma 5520A IGNITION SWITCH.doc (326.5 KB, 33 views)
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Last edited by portland_bill; 08-02-2019 at 10:30.
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Old 25-02-2019   #12
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Re: Key won’t turn in its slot

Thanks very much for your advice, ignition switch document, link and kind offer of assistance.

I bought European Breakdown Cover and we enjoyed 5 days motoring around Belgium and France.

The Croma keyfob always turned (and the car always started) second time, except it did turn first time - when starting to get off the ferry (both ways) and once when it had been left parked outside for several hours in sunlight.

As suggested in the link, thanks g8rpi - I now think that the problem is associated with the temperature of the TEG reader (the ignition key control switch unit / module / node) in the centre console. The Croma keyfob turned first time when the TEG reader was warmer – as in the warm hold of the ferry and when warmed by the sun.

When cold I now sometimes have to insert / push the keyfob into its slot three times before being able to start the car.

I’m trying to source a new Ignition Switch (TEG reader).

Part numbers are 735398770, 735431280.
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Old 25-02-2019   #13
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Re: Key won’t turn in its slot

Quote Originally Posted by uksdsgl View Post
Thanks very much for your advice, ignition switch document, link and kind offer of assistance.

I bought European Breakdown Cover and we enjoyed 5 days motoring around Belgium and France.

The Croma keyfob always turned (and the car always started) second time, except it did turn first time - when starting to get off the ferry (both ways) and once when it had been left parked outside for several hours in sunlight.

As suggested in the link, thanks g8rpi - I now think that the problem is associated with the temperature of the TEG reader (the ignition key control switch unit / module / node) in the centre console. The Croma keyfob turned first time when the TEG reader was warmer – as in the warm hold of the ferry and when warmed by the sun.

When cold I now sometimes have to insert / push the keyfob into its slot three times before being able to start the car.

I’m trying to source a new Ignition Switch (TEG reader).

Part numbers are 735398770, 735431280.
The problem with changing the TEG s unless you buy a new one from Fiat, you have to change other parts of the CODE system with units all from the same car. I can't find firm information on which units have to be changed, but it seems to be at least the keys & steering lock, probably the engine ECU, possibly the body computer. I may be able to gave more info on the body computer as I'm awaiting delivery of a spare one due to a faulty fuel gauge.

If it wasn't for the time involved with the car off the road I'd suggest you send the TEG to me and I'd change the capacitor(s).

Robert G8RPI.
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Old 25-02-2019   #14
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Re: Key won’t turn in its slot

Quote Originally Posted by g8rpi View Post
The problem with changing the TEG s unless you buy a new one from Fiat, you have to change other parts of the CODE system with units all from the same car. I can't find firm information on which units have to be changed, but it seems to be at least the keys & steering lock, probably the engine ECU, possibly the body computer. I may be able to gave more info on the body computer as I'm awaiting delivery of a spare one due to a faulty fuel gauge.

If it wasn't for the time involved with the car off the road I'd suggest you send the TEG to me and I'd change the capacitor(s).

Robert G8RPI.
The key code is held in four places. The TEG reader (ignition switch), the Steering column locking unit, the engine management computer and the body computer. Details are in the document I atteched to post #11 , but is a long tedious read.

Couldn't find anything in MES about re-coding the TEG, so didn't try. Doubtful Fiat will re-code either, as they would always prescribe new components, not used, even after parts are discontinued.
If teh problem is the microswitches, they can be replaced from another unit, if anyone is good at soldering onto circuit boards.
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Old 26-02-2019   #15
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Re: Key won’t turn in its slot

Hi Bill,
Yes I saw that the description says the TEG checks with the Body Computer, but there is nothing in eLearn about any process for fitting a new BC. It says the TEG an NBS have to be supplied pre-progrmmed to your car from the factory but does not say anything about the BC or ECU. MES has a facility for coding keys to a TEG but it's not clear if this will also code a TEG and BC together.

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