Question: I own two 2004 GM vehicles, an Impala and a Silverado pickup. The owner's manual for both states that if you move the radio from one vehicle to another, it will not work, as the radio learns the VIN of the wrong vehicle. But the Chilton repair manual for both vehicles states that if you disconnect the battery, the stereo will not work after reconnecting the battery and will read "LOC" unless you have a code. The dealer knows nothing. I need to replace batteries soon.
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Answer: You must have spoken to a salesman at the dealership, as any technician or service advisor should've been able to answer the question. And your Chilton manual information may be off by a year or two (factory service manuals are the way to go). GMs Theftlock (antitheft system) installed in certain pre-2003 vehicles will display "LOC" on the radio face and disable radio operation, when battery power is lost. Then a security code (included at vehicle purchase) is required to reactivate the radio. Often, vehicle owners lose the code or never receive one from a previous owner. In that situation, you can obtain the security code from a dealership, for a fee. Your 2004 Chevy car and truck are equipped with an updated Theftlock system. You no longer have to worry about the radio when disconnecting the battery. The new system does not require a security code; instead it electronically matches a partial VIN number stored in both the radio and a control module located elsewhere in the vehicle. If you remove the radio from one car and install it in another, the VIN information in the radio will not match that of the control module. The radio will then display "LOCKED" and become inoperable. The only way to have the radio's or the module's identification information reprogrammed is at the dealership, by a technician with a scan tool (Tech 2).
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