What are the reasons for an automatic transmission not moving when engaged?

[CalebFitz]

Automatic transmission not moving when engaged is caused by leakage in the automatic transmission oil pan, looseness in the linkage or cable between the manual valve operating handle and the rocker arm, or blockage in the oil pump inlet filter screen. Leakage in the automatic transmission oil pan: If only a small amount of hydraulic oil flows out from the pressure measuring hole of the main oil circuit, and the oil pressure is very low or almost nonexistent, it indicates leakage in the automatic transmission oil pan, causing the vehicle not to move. Open the oil pan and check if the oil pump inlet filter screen is blocked. If there is no blockage, it means the oil pump is damaged or there is severe leakage in the main oil circuit, and the automatic transmission should be disassembled. Looseness in the linkage or cable between the manual valve operating handle and the rocker arm: If the linkage or cable between the manual valve operating handle and the rocker arm is loose, the manual valve remains in the neutral or parking position. If it is loose, reassemble it and readjust the position of the operating lever. Blockage in the oil pump inlet filter screen: If there is some oil pressure in the main oil circuit when starting the cold engine, but the oil pressure drops significantly after the engine warms up, it indicates excessive wear in the oil pump, and the oil pump should be replaced.

[McIris]

Automatic transmission not moving is indeed tricky. I've driven automatic cars for many years and often encountered this issue. The most common causes are: transmission fluid level too low – power transmission fails when oil is insufficient; engine not started or running poorly, with no response when pressing the accelerator; parking brake not properly released or stuck, especially after rain or in cold temperatures. Electronic control unit failures, such as gear position sensor malfunctions, are also common, where the computer misreads the position and fails to deliver power. Additionally, torque converter leaks or gear wear can cause power to not be transmitted. It's recommended to first check the basics: ensure the engine is running, the parking brake is released, and the gear is indeed in D. If the problem persists, don't force it to avoid further damage – get it repaired promptly. Regular maintenance, such as oil changes and inspections, can prevent most faults.

[Randy]

That day I was driving to work, put it in D gear but the car wouldn't move - I was so anxious. Later I realized I'd forgotten to release the handbrake, and it worked fine after releasing it. A friend's car once couldn't move because the transmission fluid had all leaked out, and the mechanic said regular checks are crucial. Sometimes if the engine isn't warmed up enough during cold starts, gear shifting can be sluggish; or it could be a differential issue where the front wheels lock up and won't pull. Brake systems clogged with mud can also cause sticking. My personal experience is - don't stomp on the gas pedal first to avoid damaging more components. Try restarting the engine or shifting gears. If that doesn't work, seek professional help - safety first. Usually when washing the car, pay extra attention to cleaning the undercarriage.

[DeSarah]

Automatic transmission failure has multiple root causes. The torque converter is a critical component—it relies on hydraulic pressure to transfer power; low or degraded fluid renders it ineffective. Faults in the electronic control module prevent the computer from recognizing gear commands, such as when sensors malfunction. Seized transmission gears or broken chains can also cause wheel unresponsiveness. Simple self-checks like inspecting fluid levels and listening to engine sounds allow preliminary diagnosis. Severe cases require diagnostic tools to read trouble codes, often involving complex repairs. Understanding these mechanisms helps avoid misuse and enables timely repairs to prevent costly expenses.