Your '04 is too new to unlock on your own.
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
later models.
Theftlock I - Uses a volatile user settable 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. But with the correct procedure the owner can unlock it.
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 in the body control module. 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.
The dealer will use a TECH 2 scanner 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.
Thank you for using fixya, you can try removing the fuse to your radio for 5 min and reconnect it. This will reset the radio back to default and re-read the Vin number to the PCM to match with the radio. At most time this will get your radio working again and all you have to do is to re program the pre-set and clock.
How can I remove Radio from Montana 2004 ( or were is locations of screws to undo the trim of radio and panal under the radio and coffe cup holder ) so I can replace to radio
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