There are 2 types of GM Theftlock, Theftlock I and Theftlock II.


The Theftlock I is found in pre 2000 vehicles and Theftlock II is

in the latter models.


Theftlock I - Uses a volatile code that is input through the key

pad on the front of the Radio. If the power is lost (dead battery

etc.) the code is gone and must be re-entered for the radio to

work.


If you do not have the code, you can get it by phone, email, etc.

but you will need the 6 digit Radio ID number.


To get that, just turn on the ignition and hold down the 2-3 keys

(sometimes 1-4) and the first 3 digits will appear in the display.

Then hold down the AM/FM button and the last 3 digits will

show up.


With this number you can get the unlock code. This code is

available all over the place for less then $10.00. Just search

on theftlock. Use the HR and MIN buttons to enter the code

and you are in business.


This may sound a bit complicated at first but you can do it

in less then a minute with a little practice.


Theftlock II - Uses an EPROM (erasable/programmable

read only memory) or a PROM (the difference is you can

not alter the prom once it is programmed). In either case

the code is burned in and holds even when the power is lost.


With Theftlock II the radio is married to the vehicle by way

of the VIN. When the vehicle is started the computer

compares the number in the radio with the VIN. If they

match, the radio works, if not the radio displays LOC and

you are finished, there is no easy way around it. The radio

will not work until you make a trip to the dealer.


If the radio has an EPROM the dealer will use something called

a TECH 2 DEVICE to change the VIN stored in the Radio.
 
The Radio does not need to be removed (for the serial

number or any other nonsense). The technician just plugs

into the computer and resets the VIN in the radio. It can

be done (if you know how) in less then 15 minutes.

I checked around and the going rate is about $60.00


That works out to $240.00 per hour, but still much

cheaper then a new GM Radio.


If the radio has a PROM then the chip must be changed

and that seems to be factory only, in other words a new

radio! The good news is, only a very few of the high end

GM vehicles are equipped with a PROM so it is highly

unlikely that your radio has this anti theft feature.


Good Luck!