Car has been running fine. Parked and locked from the inside, not with remote. Few hours later unlocked with remote and car will not start, not even a click. Have checked all connections, wires, fuses everything. Chip in key is loose so we had the Buick dealership cut a new key. After that it started once only to shut down immediatey like the fuel just shut off. I feel this is a security system issue but do not know where to start to fix it.

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I just wrote a repair for a guy to replace the passlock sensor, but it doesn't sound that extreme. Your key has a chip in it for the passlock security system, there are 13 different resistences for these chips. Make apsolutely sure the key you had cut, has the same coded resistence (eg. code 2 will turn the cylinder of a code 3 ignition, but will shut down in a few seconds.) If you have a code 2 key make sure you order a code 3 key before you have it cut. All 13 different keys can be cut to be able to turn in the ignition but only the right code will stay running.