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Q: Thief Lock shuts off fuel or spark? on 2003 GMC Sierra 2500 HD

Thief Lock flashing on dash, eng cranks but no spark. Truck was stolen and had to put new engine in it. Want to know if the Thief Lock is the problem or a problem with ign system. It has no codes.
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It sounds like you may be having problems with your passkey system. Did you replace the ignition switch? The easy start would be to put the key in the ignition and turn it to run for about 3 seconds. Now release the key from the start position and let the vehicle sit with the key on engine off for 10 minutes no less. this will relearn your passkey. After 10 minutes turn the key to the off position then try and start the truck again. Be sure your battery is fully charged before starting. I know you said there are no codes but did you check the theft deterrent module for codes or just the powertrain control module?
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