Got a preowned 2004 318i executive series E46 facelifted two months ago, comes with 2 sets of ignition key with remote on fob. Suddenly, 1 key that can operate the keyless entry will not start the engine. Its just silent but with all the lights, horn, radio working, nothing happens when I switch it to turn on the engine. I thought its a computer problem or a battery problem (comes with newly replaced battery, AC Delco brand. I tried using the other set of key and voila, the car started. But when I alighted the car and press the remote to locked the car, nothings happens, so I manually locked the car. What seems to be the problem? Low batt on the other? and chip problem on the other one? Need your advise on this. Cause I already called 2 dealers, and they asked me to bring the unit for analysis?

There is a possibility that your key fob might lost the programming. I suggest that you re-program your key fob, follow the next steps to re-program it.

Instructions

1. • 1 Sit in the vehicle and close all the doors. Insert the key into the ignition.
     
   • 2 Turn the key to the "Off" position then to the "On" position. Repeat this until the door locks cycle to indicate that the programming mode is activated. End with the ignition key in the "On" position.
     
   • 3 Press the "Unlock" or "Lock" button on the programmable remote. Listen for the doors to lock or unlock to verify successful programming.
     
   • 4 Turn the ignition key to the "Off" position. Listen for the door locks to cycle to indicate that you have exited the programming mode.
     
   • 5 Repeat the above steps to add any additional remotes.
     

Read more : http://www.ehow.com/how_7446180_program-key-fob-kia-optima.html

in what way do you mean. is the remotes not working or are they another set? original set you turn key in ignition to number 2 and press the fob. (remote) then the doors should lock press again to unlock and turn key back to 0 and try fob again do this for both. make sure the batteries are new in the fob's. leave ignition off for 3 min before doing the other one.

Does the red light on the remote light up when you push any of the button
if no, replace remote
if yes, then try repograming the remote to the car again.
-Have remotes' ready. if you have two then fob#1 and fob#2 (doesn't matter which one is #1 or #2)
-each step has to be done within 5 sec or it will not work, but don't do it super fast.
1.turn key just to the "on" position (not starting) and push "lock button " on fob#1 once and release
2.turn key off
3.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
4.turn key off
5.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
6turn key off
7.turn key just to the "on" position (not starting) and push "lock button " on fob#1 twice (if you only have one fob, then stop here and go to step 8)and push the "lock button" on fob#2 twice.
8.turn key off and remove key from ignition.
if you did it right, remotes' should work again.
good luck

First thing, does the red light on the remote light up when you push any of the button
if no, then replace battery inside remote
if yes, then try repograming the remote to the car again.
-Have both remote ready. fob#1 and fob#2 (doesn't matter which one is #1 or #2)
-each step has to be done within 5 sec or it will not work, but don't do it super fast.
1.turn key just to the "on" position (not starting) and push "lock button " on fob#1 once and release
2.turn key off
3.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
4.turn key off
5.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
6turn key off
7.turn key just to the "on" position (not starting) and push "lock button " on fob#1 twice (if you only have one fob, then stop here and go to step 7)and push the "lock button" on fob#2 twice.
8.turn key off and remove key from ignition.
if you did it right, remotes should work again.
good luck

Key Fob Auto Learn
This procedure will first erase all known key fobs. The procedure will then program a single or multiple key fobs. Method 3 is a series of three 10-minute key cycles, for a total of 30 minutes. This procedure requires that you have a replacement key fob and the vehicle mechanical key.

Important: All previously programmed key fobs will be erased upon completion of the 30-minute programming procedure. The order in which the key fobs are programmed will determine its numbering position within the RCDLR memory. The first key fob programmed will be key fob #1, and the second key fob programmed will be key fob #2. The number stamped on the key fob case is for reference only: #2 can be programmed as #1.
Do not place any known good key fobs in the vicinity of the vehicle when programming. 

The vehicle must be OFF. 
Place the replacement key fob in the console pocket with the buttons facing forward. 
Insert the vehicle key in the driver door lock cylinder located in the driver door handle and cycle the key 5 times within 5 seconds. 

The DIC will display a message: OFF/ACC TO LEARN. 
Press the OFF/ACC portion of the ignition button. 
The DIC will display a message: WAIT 10 MINUTES, then it will count down from 10 to 0, one minute at a time. 
When the counter reaches 0, DIC will display OFF/ACC TO LEARN. 
Repeat steps 5-7 two more times, for a total of 30 minutes. 
The DIC will display a message: OFF/ACC TO LEARN. 
Press the OFF/ACC portion of the ignition button. 
A beep will occur and the DIC will display: READY FOR FOB 1. At this time all previously known key fobs have been erased. When fob 1 is programmed a beep will be heard and the DIC will display a message: READY FOR FOB 2. 
Additional key fobs can be programmed by taking fob 1 out of the pocket and inserting fob 2. If desired, up to 4 fobs can be programmed. Once 4 fobs have been learned, the DIC will display a message: MAX FOBS LEARNED, and automatically exit the program mode. 
If learning less than 4 key fobs, press the OFF/ACC portion of the ignition button to exit the program mode. 
Operate the active portion of each key fob in order to finalize the programming sequence and verify correct system operation. 

Good luck and hope this help's keep me posted, there are 3 other methods and the 5th method is a tech 2 scan tool that the dealer uses but this should work on your year of cadillac. 

Manual Programming Procedure (non scan tool)
1. Connect pin 1 of the 16-way data link connector to chassis ground or to pin 4 of the 16-way data link connector.
2. Close all doors, turn ignition key to off.
3. Turn ignition key to Accessory.
4. Turn ignition to off, door locks will cycle once (in programming mode).
5. For each key FOB, press any button 3 times in a row to program code. When programming is complete, the door locks will cycle once.

NOTE:
IF A SECOND KEY FOB REQUIRES PROGRAMMING, IT MUST BE PROGRAMMED WITHIN 1 MINUTE OF PROGRAMMING
THE FIRST FOB PROGRAMMING. PRESS ANY BUTTON ON THE SECOND FOB 3 TIMES TO PROGRAM ITS CODE. WHEN PROGRAMMING IS COMPLETE, THE DOOR LOCKS WILL CYCLE ONCE.

6. The programming mode finishes after the following:
a. Programming of two key FOBS is completed.
b. One minute has passed since programming.
c. Pin 1 of 16-way data link connector is removed from ground connection.
d. Ignition switch is turned on.
e. Any of the doors are opened.

VW/AUDI/SEAT/SKODA



Remote Control Programming (1997 ON)

Procedure
1. Switch Ignition ON and leave the key in the ignition.

2. Mechanically lock the vehicle using the Drivers door using a second
key.

3. Using the remote control press the Unlock button once, and the horn
will sound once.

4. Wait 6 seconds and press the unlock button once to activate the coding
procedure. The remote control will now be programmed.

NOTE : When performing programming on additional remotes the procedure
is the same, except you press the unlock button 2, 3 or 4 times for the
different remote.

For example : If programming 2 remotes press the unlock button twice with
a 1 second interval between each press, repeat for 3 and 4 remotes.

5. Switch Ignition OFF.

6. Remove key from ignition and check for operation.

7. The coding procedure can be repeated up to 4 times for additional remotes.

8. The ignition must be switched OFF between programming each remote
control.

Remote Control Erasing (1997 ON)

Procedure
1. Switch Ignition ON and leave the key in the ignition.

2. Mechanically lock the vehicle using the Drivers door using a second
key.

3. Press the remote control unlock button 5 times in 1 second intervals.
A short horn will sound.

4. Wait 6 seconds and press the unlock button once to activate memory
erase.

5. Switch ignition OFF, all remotes are now erased.

I have an A4 and did this to re-program my key:

1. used the key to start the car...then turned it off
2. put the key in the driver door (door closed)
3. pressed the lock button on the key fob once
4. turned the key to lock the door.

This is basically the steps in the owners manual, but the car must be started with the key first, and the key must be in the door lock before pressing the lock button.

2000 Mazda 626
Note: Make SURE the battery is new.
Instructions for programming ONE keyless remote fob.
1. Open the driver’s door & leave open.
2. Insert the key in the ignition.
3. Turn the key to the on and off position 3 times.
4. Remove the key from the ignition.
5. After door open chime stops, press the door open button 3 times.
6. After chime, press any fob key twice.
7. After second chime, press any fob key twice again.
8. After third chime, press any fob key twice again.
9. Press the door open button once.
10. The car should give another acknowledgement chime.
11. Test key fob.
This DOES work. I just programmed mine successfully today, three hours ago.