Possible reasons why an automatic transmission may reset a gear:
1. Transmission fluid level is low:
* Check the fluid level and add if necessary.
2. Contaminated or old transmission fluid:
* Replace the transmission fluid along with the filter.
3. Worn friction linings:
* Gears may slip, causing the gear to be reset. The transmission needs to be repaired.
4. Malfunction of solenoids:
* Solenoids are responsible for turning gears on and off. Replace faulty solenoids.
5. Transmission control module (TCM) malfunction:
* The TCM controls the electronic components of the transmission. Replace the faulty TCM.
6. Malfunction of the engine speed sensor or vehicle speed:
* These sensors provide information to the TCM about engine and vehicle speed. Replace faulty sensors.
7. Wiring harness fault:
* An open or short circuit in the transmission wiring harness may cause the transmission to reset. Repair or replace faulty wiring.
8. Torque converter malfunction:
* The torque converter is responsible for transferring engine power to the transmission. Replace the faulty torque converter.
9. Malfunction in the car’s electronic system:
*Other electronic systems in the vehicle, such as the engine management system, may affect transmission performance. Carry out diagnostics of electronic systems.
10. Mechanical transmission problems:
* Worn gears, bearings or other internal components may cause the transmission to reset. The transmission needs to be repaired.