General Key fob not locking

[Kimmykt]

Hello, I’m a newbie here I have a 63 plate Fiat 500. A few months ago I lost the key fob to my car whilst I was moving business premises, I found it about 6 weeks later in a box. So for 6 weeks or so I was having to use the spare manual key. However once I found the master key it wouldn’t lock the doors through the central locking . It would start the engine. I took it to a friend who owns a locksmith’s he tested the battery in the fob and said it was fine.

Am I right it thinking it could just be a case of the fob having lost communication with the brains of the car and needs to be reset. If so is that easy to do and can I do it myself (I read something similar on a previous thread)

My mechanic is telling me it could be an electrical problem and quite expensive to fix but I can’t see that myself

TIA

 

[s130]

Is the spare manual key is operating the central locking? Also you can manually check the central locking system. Lower the drivers and passengers windows. With all doors closed (inc. tailgate) opertate them both using any locking/unlocking buttons you have inside the car. On my 500X I have two electrical buttons (lock & unlock) and a mecanical close/open lever/rocker. Both will operate the central locking, but for the electrical button I think the ignition has to be on.

If this is working all OK then the fault is most probably with the fob / receiver. If not then it isprably with the door locks and/or wiring.

Sticking locks/solenoids with stop the central locking working as will a broken door wire.

It is a matter of checking all ways of exciting the locking system and noting the responses. Sometimes the passenger door controls will unlock the car but not lock. Sometimes the driver's door will lock and unlock but not trigger the passenger side.

As always it is best to replace the fob battery. Battery testers are a guide as they put a nominal load on the battery, usually a small load, and then rely on the measured voltage. This is often not good enough.

Also the key fobs use a hopping code where the code sent each time is different. The car keeps a rolling log of the code last used. When a new code is sent it will check to see if the code is then next expected one. If not it may do a "look ahead". I've had a key fob get out of sequence with the car due to being pressed in my trouser pocket whilst out of range of the car. Using a second remote or operating the original remote multiple times will get the system back in sync.

I've never understood/researched why using a second key should reset the sync with the troubled key but this may be a "get you out of trouble quickly" security feature in that the car does not expect both keys to go effecticly missing at the same time some accepts the second key as indicating all is well and it is just a sync problem so then takes the next code from the bad fob ang resets the hopping table.

 

[Kimmykt]

Is the spare manual key is operating the central locking? Also you can manually check the central locking system. Lower the drivers and passengers windows. With all doors closed (inc. tailgate) opertate them both using any locking/unlocking buttons you have inside the car. On my 500X I have two electrical buttons (lock & unlock) and a mecanical close/open lever/rocker. Both will operate the central locking, but for the electrical button I think the ignition has to be on.

If this is working all OK then the fault is most probably with the fob / receiver. If not then it isprably with the door locks and/or wiring.

Sticking locks/solenoids with stop the central locking working as will a broken door wire.

It is a matter of checking all ways of exciting the locking system and noting the responses. Sometimes the passenger door controls will unlock the car but not lock. Sometimes the driver's door will lock and unlock but not trigger the passenger side.

As always it is best to replace the fob battery. Battery testers are a guide as they put a nominal load on the battery, usually a small load, and then rely on the measured voltage. This is often not good enough.

Also the key fobs use a hopping code where the code sent each time is different. The car keeps a rolling log of the code last used. When a new code is sent it will check to see if the code is then next expected one. If not it may do a "look ahead". I've had a key fob get out of sequence with the car due to being pressed in my trouser pocket whilst out of range of the car. Using a second remote or operating the original remote multiple times will get the system back in sync.

I've never understood/researched why using a second key should reset the sync with the troubled key but this may be a "get you out of trouble quickly" security feature in that the car does not expect both keys to go effecticly missing at the same time some accepts the second key as indicating all is well and it is just a sync problem so then takes the next code from the bad fob ang resets the hopping table.

Thank you very much I’ll try the above