Possible reasons for the loss of reverse gear on the AF17 automatic transmission:
Mechanical problems:
* Worn or damaged transmission components such as reverse gears, synchronizers or differential.
* Defective drive shaft or axle shaft.
* Problems with the vehicle speed sensor or reverse sensor.
Electrical problems:
* Faulty reverse solenoid.
* Break or short circuit in the wiring or automatic transmission connectors.
* Problems with the automatic transmission control module (TCM).
Other reasons:
* Insufficient transmission fluid level or incorrect fluid used.
* Worn or malfunctioning hydraulic controller (TCC).
* Weak battery or electrical system problems.
Diagnosis and troubleshooting:
1. Check the level and condition of the transmission fluid. Add fluid as needed and check for metal particles or foreign matter.
2. Scan trouble codes using an OBD-II scanner. Codes may indicate specific faulty components.
3. Carry out a mechanical check. Inspect the drive shaft, axle shafts, and other transmission components for damage or wear.
4. Check electrical components. Examine the condition of the solenoids, wiring and connectors.
5. If available, perform diagnostics using a professional automatic transmission scan tool. This can provide additional information about the condition of the transmission.
Solution:
Depending on the identified cause, the following may be required:
* Replacement of faulty transmission units
* Repair or replacement of electrical components
*Hydraulic regulator adjustment
* Replacing the battery or solving problems with the electrical system
Note: Reverse gear loss is a serious problem that can affect the safety and handling of the vehicle. It is not recommended to operate a vehicle with a faulty reverse gear. Have it diagnosed and repaired by a qualified mechanic as soon as possible.