* Transmission Problems: This is the most likely culprit. The issue could be:
* Low Transmission Fluid: Check the transmission fluid level. If it's low, you might have a leak somewhere in the system. Low fluid can cause catastrophic transmission failure. Important: Check the fluid's condition; it shouldn't be burnt or smell foul.
* Transmission Fluid Filter: A clogged filter restricts fluid flow, preventing proper shifting.
* Internal Transmission Problems: This could range from worn clutches and bands to more serious internal damage requiring a rebuild or replacement. This is often indicated by strange noises, slipping, or hard shifting *before* it completely stopped shifting.
* Shift Linkage or Cables: (Less likely on this model year, as it likely has electronic shifting) In older cars with manual shift cables, these can break, become disconnected, or bind. This is less likely on a 2000 Malibu.
* Solenoids/Valves (Automatic Transmission): These electrical components control fluid flow within the transmission. A faulty solenoid can prevent gear engagement. A scan tool is needed to diagnose this.
* Torque Converter: While less common as the initial problem, a faulty torque converter can prevent the transmission from engaging.
* Shift Interlock System: This prevents the car from starting unless it's in Park or Neutral. However, if the car runs, this is probably *not* the primary problem, but it could be contributing if it's malfunctioning.
* Other Electrical Issues: While less likely, a problem in the car's electrical system could be interfering with the transmission's controls.
Troubleshooting Steps:
1. Check the Transmission Fluid: This is the absolute first step. Find the dipstick (often marked with "Trans" or a gear symbol) and check the fluid level while the engine is running and warmed up (but not excessively hot). If low, add the correct type of ATF (Automatic Transmission Fluid) for your vehicle. If the fluid is burnt or smells foul, you have more serious problems.
2. Inspect for Leaks: Carefully examine the transmission for any leaks around the pan, lines, or seals.
3. Check the Shift Lever: Make absolutely sure the shift lever is actually in the "Drive" position. Sometimes it can feel like it's engaged but isn't.
4. Scan for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any trouble codes stored in the car's computer. This can provide valuable clues about the problem. Auto parts stores often offer free code reading.
5. Professional Diagnosis: If the above steps don't reveal the problem, it's time to take the car to a qualified mechanic or transmission specialist. They have the tools and expertise to diagnose the issue accurately and perform necessary repairs.
Important Considerations:
* Driving the Car: Do *not* attempt to force the car to shift or drive if it's not engaging properly. This can cause further damage to the transmission.
* Towing: If you suspect significant transmission damage, having the car towed to a repair shop is recommended.
The transmission is a complex system. Professional diagnosis is often necessary for accurate repair. Don't delay getting it checked, as further driving with a transmission problem can lead to costly repairs.
