Make sure the battery isn't dead. But trunk should open with dead battery. It uses vacuum for the trunk lock as well as mechanical linkage. Rotating the key all the way around counterclockwise and holding it there and then pressing in on the lock overrides the vacuum linkage. If that doesn't work your looking at drilling it out. Also some cars have valet keys that won't open the trunk make sure you not using one of those.
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Make sure the battery isn't dead. But trunk should open with dead battery. It uses vacuum for the trunk lock as well as mechanical linkage. Rotating the key all the way around counterclockwise and holding it there and then pressing in on the lock overrides the vacuum linkage. If that doesn't work your looking at drilling it out. Also some cars have valet keys that won't open the trunk make sure you not using one of those.