* Neutral safety switch issue: The neutral safety switch is a safety feature that prevents the engine from starting if the transmission is not in park or neutral. If this switch is faulty, it can also prevent the transmission from shifting out of park.
* Transmission control module (TCM) issue: The TCM is the electronic control unit that oversees the operation of the transmission. If the TCM is malfunctioning, it can cause the transmission to shift erratically or not shift at all.
* Low transmission fluid: Low transmission fluid can cause the transmission to overheat and malfunction, which can prevent it from shifting out of park.
* Internal transmission damage: If the transmission itself is damaged, it may not be able to shift out of park. This is typically the most serious cause of this problem, and will likely require professional repair.
