Steps to Diagnose Automatic Transmission Problems
1. Check the level and condition of the transmission fluid
* Check the fluid level with the engine running and the automatic transmission selector in Park (P).
* Check to see if the liquid is dark or smells like burning. These are signs of contamination or overheating.
2. Scan trouble codes
*Use an OBD-II scanner to check for automatic transmission related trouble codes.
* Decipher the codes and refer to the appropriate repair manual.
3. Inspect the automatic transmission
* Inspect the transmission for leaks, rust or damage.
* Check the condition of moving parts such as the torque converter clutch and shafts.
4. Check the pressure in the automatic transmission
* Connect a pressure gauge to the port to check the automatic transmission pressure.
* Compare the measured pressure with that specified in the repair manual.
5. Perform a slip test
* Accelerate the car in D or S mode.
*Note for slipping or fluctuation in engine speed, which may indicate worn friction plates.
6. Check the transmission control module (TCM)
* TCM is an electronic component that controls the operation of the automatic transmission.
*Check for trouble codes related to the TCM and replace it if necessary.
Common automatic transmission problems
*Slippage
*Hard shifting
* Fluid leaks
* Overheating
* Electronic system malfunctions
* Worn friction discs
*Damaged gears or shafts
Tips for diagnosing automatic transmission problems
* Be precise and consistent when performing diagnostic steps.
*Refer to the repair manual for your specific vehicle make and model.
* Use quality diagnostic tools.
*If the problem persists, contact a qualified mechanic.