Possible reasons why the engine stalls when the automatic transmission is engaged:
1. Problems with the transmission mechanism
*Low ATF level
* Too dirty or old ATF fluid
*Clutch slippage
* Wear or damage to gearbox parts
2. Electrical problems
* Malfunction of the throttle position sensor
* Malfunction of the mass air flow (MAF) sensor
* Malfunction of the crankshaft position sensor
* Problems with wiring or connectors
3. Mechanical problems
* Clogged fuel filter
* Air filter clogged
* Fuel pump malfunction
* Malfunction of the catalytic converter
* Oxygen sensor malfunction
4. Software problems
* Failures in automatic transmission software
* Incorrect transmission calibration
5. Other
* Engine wear or damage
* Vacuum loss
* Exhaust system malfunction
What to do:
* Check the level and condition of the ATF fluid.
* Diagnose trouble codes (DTCs) using an OBD2 scanner.
* Check mechanical components such as filters, hoses and connections.
* Make sure electrical components such as sensors and wiring are in good condition.
* Check the automatic transmission software and update it if necessary.
*Consult a qualified mechanic for further diagnosis and repair.