Possible reasons for loss of automatic transmission reverse speed:
Mechanical problems:
* Wear of reverse clutches
* Damage to reverse gears
* Worn or broken reverse gear piston
Hydraulic problems:
* Faulty reverse solenoid
*Low transmission fluid level
* Contaminated transmission fluid
* Valve unit malfunctions
Electronic problems:
* Faulty gear selector position sensor
*Wiring problems
* Faulty electronic transmission control unit (ETCU)
Other possible reasons:
* Worn input shaft bushing
* Faulty oil pump
* Worn oil filter
* Dirty automatic transmission pan
Recommended actions:
1. Check the transmission fluid level and add it if necessary.
2. Check the electrical wiring for damage or breaks.
3. Read fault codes from the computer using a diagnostic scanner.
4. Check the operation of the reverse solenoid using a pressure gauge.
5. If no mechanical or hydraulic fault is found, the ECU may need to be replaced.
Important: Do not operate the vehicle with a missing reverse gear, as this may cause additional damage to the transmission. Contact a qualified mechanic for diagnosis and repair.