The 3-button fob will unlock the doors just fine, but will not lock them. The red LED indicator illuminates when the lock button is pressed. Could this be a faulty fob, or should I suspect something with my vehicle?

 

it'sprobably be your lock relay is not working. the system uses two relays one for lock the other for unlock. sometimes one work without the other.

 

Or it could be a problem with the alarm. Are you sure all the doors, hood, and trunk are fully closed? If one not fully closed and the switch isn't pressed, the alarm will not arm (and I think the locks will not lock).

 

if the hood or the trunk is not closed properly the doors will still lock but will not arm the alarm system.

 

Okay. Could you tell me where to find those relays on my 02 Sonata, so I can check 'em? [/align] [/align]

I got it. Found info elsewhere on the forum here: https://www.hyundaiforum.com/m_295/tm.htm
[/align]

 

you have to remove the under dash/under steering wheel. when you remove it, remove metal guard, remove fuse box, behind fuse box there are two white relays one is for lock the other is for unlock.

 

Thanks, madindian1 [/align]

 

no problem like my signature says