Sunday, June 12, 2011

How does the ignition key pellet works in the ignition switch of the car?

The lock cylinder has two wires that run down the steering column. The key is inserted into the lock cylinder and the contacts send the resistance reading of the pellet to the theft module. If the key pellet resistance matches what is learned into the theft module , the starter will turn. If not it wont and will start a 4 minute timer. ( nothing will work during this time) If you continue turning the key to start , 4 min will be added each key turn.

So the timer has to run out. ( It takes allot of patience to work on this system)

How to test the lock cylinder and wires. used a ohm meter to read the key pellet resistance. ( write it down) disconnect the connector at the bottom of the steering column ( orange wire connector ) insert the key in the lock cylinder and check the resistance at the bottom of the steering column connector that goes back up to the lock cylinder. While you are watching the meter, Turn the key to start. ( Does the resistance match your first reading, through the key cycle?)

This reading has to stay the same !!!

If this reading is changing, so is the signal being sent to the theft module, and it will arm the system if it does not match the resistance code in the theft module.

Since this is the most likely area for things to go wrong, ( wires strands break, connection get poor) I would have the lock cylinder replaced first.

Now why a used module will be more trouble than you will save.

As I mentioned earlier, the theft module learns the first key code it is exposed to. There are 15 key codes. So to find out what code a module has, you need to use a VATS interrogator. It has all 15 codes in it, and you start with one and try to start the engine. If it turns over then thats the code. If not then you have to wait till the timer runs out and try the next code, until you find the correct code. This could take a while, or be found in 10 minutes.

After you find the code, then you have to cut new keys to that code. ( these keys are expensive) so the savings in parts may be lost with all the extra steps needed to get a used module to work.Plus the cost of new keys.




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