1. Fluid Level and Condition:
* Check the transmission fluid level: This is the absolute first thing to do. Low fluid can cause all sorts of transmission issues. Find the dipstick (usually marked with "ATF" for automatic transmission fluid) and check the level when the engine is running and warmed up (ideally at operating temperature).
* Check the transmission fluid condition: Is it the correct color (should be reddish-pink, depending on the type of fluid)? Is it burnt (smells burnt, dark brown or black)? Dirty or burnt fluid indicates serious problems and needs immediate attention.
2. Shift Linkage/Selector Cable:
* Inspect the shift linkage: Ensure the linkage connecting the gear selector lever to the transmission is properly adjusted and not damaged or disconnected. A loose or broken cable could prevent the transmission from selecting forward gears. This is less likely if reverse works, but worth a quick visual check.
3. Transmission Solenoids and Valve Body:
* Internal transmission problems: This is where it gets more complex and likely requires professional diagnosis. Problems with the valve body (which controls fluid flow) or solenoids (electromagnetic switches that operate the valve body) are common causes of gear selection problems. A faulty solenoid related to forward gears could explain the symptom. This usually requires specialized tools and knowledge to diagnose and repair.
4. Torque Converter:
* Torque converter issues: A faulty torque converter (the component that connects the engine to the transmission) could prevent the transmission from engaging forward gears. Diagnosing this requires specific testing procedures.
5. Low Input Shaft Speed Sensor:
* Sensor failure: This sensor monitors the engine's speed. A faulty one can prevent the transmission from engaging.
6. Other Electrical Issues:
* Wiring harness: Check for any damaged or corroded wires in the transmission wiring harness.
What you should NOT do:
* Attempt any major repairs yourself unless you have significant mechanical experience with automatic transmissions. This is a complex system, and improper repair can lead to catastrophic damage.
* Continue driving the car. Driving with a malfunctioning transmission can cause further damage and potentially leave you stranded.
What you SHOULD do:
* Have the vehicle towed to a qualified mechanic or transmission specialist. They have the diagnostic tools and expertise to pinpoint the problem and recommend the appropriate repair. Describing the symptoms (reverse works, forward doesn't) will help them diagnose the issue more efficiently. A proper diagnosis is essential before any repairs are undertaken.
