Mechanical Issues:
* Park pawl malfunction: The park pawl is a mechanical device that engages with the output shaft of the transmission to lock the wheels. Wear, damage, or breakage of this pawl can prevent it from engaging properly. This is often caused by forcing the shift lever while the car is moving or hitting something hard.
* Shift linkage problems: The linkage connecting the shift lever to the transmission can become bent, broken, or otherwise misaligned, preventing the park pawl from engaging. This could be due to age, rust, damage, or poor maintenance.
* Transmission problems: Internal transmission issues, though less common, can sometimes prevent the park mechanism from functioning. This could involve damage to internal parts or low transmission fluid.
Electrical Issues (mostly in automatic transmissions):
* Shift interlock solenoid failure: Many automatics use a solenoid to allow shifting out of park. A faulty solenoid won't release the lock, preventing shifting. This often requires replacement of the solenoid.
* Electrical wiring problems: Damaged or corroded wiring to the shift interlock solenoid or other related components can also prevent the system from functioning correctly.
* Faulty shift lever position sensor: The sensor tells the car's computer the gear selected. If it's malfunctioning, the computer might not allow the car to leave park.
Other Possibilities:
* Low transmission fluid: While not directly preventing engagement, low fluid can affect the transmission's internal pressure, making it difficult or impossible to shift into park, or to shift out of park.
* Parking brake engaged: A fully engaged parking brake can make it *feel* like the car is stuck in park, even if it isn't.
* External obstructions: Something might be physically blocking the shift lever.
* Driver error: Sometimes, the issue isn't a mechanical problem but the driver not properly depressing the brake pedal (often required to shift out of park in modern vehicles) or not engaging the key or button to release the shift lever properly.
If a car is stuck in park, it's crucial to have a qualified mechanic diagnose the issue. Attempting to force the shift lever can cause significant damage.
