Make sure the contact points on the little black chip in key are clean and ensure the chip is centered in the key. If security light goes on you must wait a few minutes for it to go off before attempting to start car again.
The computer only resets when the battery is removed. The alternator just charges the battery, so if the battery is left connected when the alternator is replaced, the computer should not reset.
did you check the alternator??
Inside the alternator
Voltage regulator or loose wire.
Check the battery cables or starter.
Alternator is not charging. Have it tested and/or replaced.
To remove the alternator from a 2004 Buick Rendezvous, first disconnect the negative battery cable to prevent electrical shock. Next, remove any components obstructing access to the alternator, such as the air intake duct. Then, disconnect the electrical connections from the alternator and remove the mounting bolts. Finally, carefully pull the alternator out of its bracket for removal.
You can have the alternator tested free of charge at just about any major auto parts store. By the way, a bad alternator will not "discharge" a battery - the alternator's function is to provide the charge to the battery. If the alternator is faulty, then it is not providing the charge necessary to keep other components from discharging the battery. I had the alternator tested and it was charging. If the alternator has a bad diode, it will discharge the battery. I replaced the alternator and everything is fine.
defective alternator
alternator needs to be replaced. battery also might be a problem due to the alternator not charging it
It could be an alternator. Check with a mechanic if that is the issue.
Voltage Regulator?