Possible causes of the automatic transmission error ‘Incorrect gear ratio’:
* Incorrect automatic transmission fluid levels: Low or high fluid levels can cause slippage or improper shifting.
* Clogged automatic transmission filter: A dirty filter prevents proper fluid flow, resulting in shifting problems.
* Faulty input shaft speed sensor: This sensor tells the automatic transmission computer the rotational speed of the input shaft, which is necessary for correct gear selection.
* Faulty output shaft speed sensor: This sensor tells the automatic transmission computer the speed of rotation of the output shaft, also necessary for correct gear selection.
* Faulty automatic transmission control solenoid: The solenoids control the flow of fluid into the automatic transmission, providing the necessary hydraulic pressure to shift gears. A faulty solenoid can cause improper shifting.
* Malfunction of the automatic transmission control unit: The automatic transmission control unit (TCU) is a computer that controls the operation of the automatic transmission. A faulty TCU can send incorrect signals to solenoids and other components.
* Automatic Transmission Mechanical Failure: A serious mechanical problem, such as a broken gear or damaged clutch, can cause an incorrect transmission ratio.
Troubleshooting steps:
1. Check the level and condition of the automatic transmission fluid: Make sure that the fluid level is correct and that the fluid itself is clean and transparent.
2. Replace the automatic transmission filter: Regularly replacing the automatic transmission filter prevents clogging.
3. Test the input and output shaft speed sensors: Measure the output voltage of the sensors and compare them to the manufacturer’s specifications.
4. Check the automatic transmission solenoids: Use a diagnostic scan tool to check the operation of the solenoids.
5. Diagnose the automatic transmission control unit: A diagnostic scanner can be used to search for trouble codes stored in the TCU.
6. Perform a visual inspection of the automatic transmission: Inspect the automatic transmission for leaks, damage or signs of wear.
7. Disassemble the automatic transmission for a deeper inspection: This may be necessary if other diagnostic tests have not found the cause of the problem.