[toodoo9011]

i was given 2 keys fobs one works fine the other i put a new battery and see red light up on the fob when a button is pressed but no reaction to the car .any ideas help please?

[Dazzler]

Welcome. Sounds like it might need reprogramming by dealer. Maybe battery was flat too long before replacement.

[toodoo9011]

is it free to program by dealer here in uk  or will it cost me?

[Dazzler]

Depend on the dealer I reckon. Shop around. How long ago did you buy it? If from a yard ask them for help maybe.

[cruiserfied]

Welcome to the club.

If the red light is working the remote "should" be ok.

My theory is the old owner may have had 1 key replaced and didnt supply the 2nd key to reprogram. Both keys are required at the same time as it wipes the memory when reprogramming.

If you have only just bought the car and it was from a yard i would be going back and requesting used car warranty/guarantee. If they supply 2 keys they should both work.
If not from a yard your best taking it to the dealer, as Dazzler said it will depend on the dealer as to how much they would charge. 1/2 hour labour would be plenty for a key reprogram assuming there are no other concerns.

[diablo]

is it free to program by dealer here in uk  or will it cost me?

I had a non-working key after they changed my ECU under warranty in 2015. I mentioned it on my last service and they said they'd re-program the spare key. Which they did, but £37.50 (plus VAT) appeared on my bill. 

I'd, perhaps foolishly, assumed it would be free. But I didn't get that confirmed at the time - and wasn't in the mood for an argument.

[eye30]

What year is your car?

Just a thought...... i wonder if the fob is for the car as some cars, mainly the very early ones , only came with 1 fob.

Also, does the fob have the hy logo on the rear of it?

[Surferdude]

What year is your car?

Just a thought...... i wonder if the fob is for the car as some cars, mainly the very early ones , only came with 1 fob.

Also, does the fob have the hy logo on the rear of it?

Says 2007 in his sig.

[eye30]

Ok so when i got my 2007 it only came with 1 key.

Complained and provided 2nd.

Had to get it programed by handing in key 1 so they could do both.

May be not programed.

[ibrokeit]

A quick 'test' you might be able to perform, to see if it is programmed or not (or maybe possibly only partially), is by using the key-fob that seems not to work to manually unlock the drivers door.   Just remember to not have two keys in close proximity to each other (per user manual)...

The alarm will, mostly likely, start sounding - but should be dis-armed once you insert the key into the ignition and start the engine (assuming the the key in question is recognised so can start the engine).  This is per the user manual...  ~Page 4-7 under 'Theft-Alarm System' - which I am assuming is quipped because it is usually present with 'Remote Keyless Entry'.

While it is likely you will need to make a trip to a service centre it might help with diagnosis - per the words of our Top Tech cruiserfied about the memory being wiped when reprogrammed (therefore both are needed)...

If the engine starts (the alarm should deactivate per user manual) then the key is recognised/programmed (at very least to some extent).   If it doesn't start (the alarm system will remain active) - then it isn't recognised/programmed to the ECU (or is it BCM? or both?) at all.  If you observe the former it may indicate a faulty 'Keyless Entry' transmitter (which is what uses the battery) or it may not; I am not sure about the idea of the battery being flat too long... however I know with some rolling-code systems if a learned 'transmitter' is too far out of sync repeated transmission bursts (i.e. button presses) will resync them - so maybe something to try (but I wouldn't place much hope in that).

The reason the key may start the car but not unlock it is the key-fob actually had two wireless transmitters - one is Active (hence the battery) for 'Keyless Entry' and has ~10m range; the other is Passive (no battery) for the 'Immobiliser System' (stops engine starting), has a range of cms and is activated by the antenna coil for it contained in the ignition.   Unlocking with keyless entry unlocks the vehicle and disables the alarm system only; inserting the key and, assuming it is recognised, turning it to ON disables the Immobiliser (and, if not done already, turning it to start disables the alarm system).

[toodoo9011]

i got a 2007 i30 with logo on back of fob.

i can open the door and start the car with it

[ibrokeit]

Okay - so it is recognised (at least by one of the systems).   I am not sure if that will change cruiserfied's advice any, but it helps narrow the symptoms.

One other quick and easy test - be warned it sounds stupid, silly and possibly insulting (by apparent implication from the action)... you could try swapping the battery from the one that works to the one that doesn't temporarily.  Though it is unlikely to have any effect what so ever it would eliminate the possibility of dud new battery - by using a battery you know is working (i.e. fault-finding technique of 'known-good' and assuming everything not proven good is faulty, even if new).  Or if you would prefer not to do that - trying another new battery if available.

I don't know what else you could try.