Possible Causes:
* Low Transmission Fluid: This is the first and easiest thing to check. Low fluid can cause harsh shifting and damage the transmission. Check the transmission fluid level (while the engine is running and warmed up) and its condition. If it's low, add the correct type of transmission fluid (consult your owner's manual). If it's dark, burnt, or smells burnt, it likely needs a complete fluid and filter change, or even more extensive repair.
* Failing Transmission Solenoid(s): These electrical components control the shifting mechanism. A faulty solenoid can cause inconsistent shifting, including hard shifts. This is a common problem in older automatics.
* Worn-out Clutch Packs or Bands: These are internal parts of the transmission that wear down over time. Severe wear can lead to harsh shifting and eventual transmission failure.
* Torque Converter Issues: The torque converter connects the engine to the transmission. Problems here can manifest as harsh shifting.
* Faulty Transmission Valve Body: This controls fluid flow within the transmission. A malfunctioning valve body can cause a variety of shifting problems.
* Other Sensor Problems: Various sensors (like the transmission temperature sensor or speed sensor) can send incorrect information to the transmission control module (TCM), resulting in improper shifting. The check engine light is likely related to one of these sensor issues.
What to Do:
1. Check the Transmission Fluid: This is the most crucial first step. If low or severely contaminated, that's a serious problem requiring immediate attention.
2. Get the Diagnostic Trouble Codes (DTCs) Read: A mechanic or auto parts store can use a code reader to retrieve the DTCs stored in your car's computer. These codes will pinpoint the specific problem(s) the check engine light is indicating. This is *essential* before doing anything else.
3. Don't ignore it: Continuing to drive the car with a hard-shifting transmission will likely cause further damage and increase repair costs significantly. The longer you wait, the more expensive the fix will be, potentially leading to a complete transmission replacement.
4. Seek Professional Help: Based on the DTCs and the fluid condition, a mechanic can diagnose the specific problem and recommend the appropriate repair. Given the symptoms, a transmission specialist might be a better option than a general mechanic.
In short: Don't delay. Get the codes read and have the transmission fluid checked immediately. Driving with a transmission problem can lead to very expensive repairs.
