* Shifting mechanism failure: This could be a problem with the linkage (cables or rods) that connect the shifter to the transmission, a faulty shift selector, or a malfunction within the transmission's internal shift mechanism. Something is preventing the transmission from selecting the correct gears beyond second.
* Valve body issues: The valve body is a crucial part of the automatic transmission. It contains valves and passages that control the flow of fluid, directing it to engage different clutches and bands for different gears. A faulty valve, a blockage, or low fluid pressure in the valve body could restrict the transmission to second gear.
* Low transmission fluid: While not directly causing it to *lock* in second, severely low transmission fluid can lead to significant internal damage and cause the transmission to act erratically, potentially restricting it to only one gear. This is more likely to cause slipping or rough shifting before complete lock-up in a specific gear.
* Internal transmission damage: This is the most likely and serious culprit. Worn clutches, bands, or other internal components can prevent the transmission from shifting properly. This could be due to lack of maintenance, age, or previous damage. A broken component could physically jam the mechanism.
* Solenoid problems: Solenoids are electrically controlled valves within the transmission. A faulty solenoid could fail to allow fluid flow needed for proper gear selection.
In short: A transmission locked in second gear is not a minor issue and requires professional diagnosis and likely a major repair or transmission replacement. Driving the car in this condition could cause further damage. You should not attempt to drive the car extensively, and should have it towed to a qualified mechanic specializing in automatic transmissions.
