your code is registering that the oil pressure sensor input is stuck on low. This can be caused by 3 things.
1 is that the sensor has failed
2 is that the wiring is damaged/corroded
3 is that the ECU is dead (not plausible in most cases - toyota ECUs are pretty dumb but live a long life)
to test the pressure sensor - first check continuity of the 3 pin pressure sensor connector to the ECU plug, Connect a good scan tool and navigate to the powertrain->engine/ect->datalisting
run test A/T oil pressure - for the secondary oil test you should see a value between 3.7 to 5.8 Mpa. If you dont see these values then check the resistances in the oil pressure sensor.
firstl verify that you get a signal of 4.5~5V at the sensor connector - the pins to test are the pins at the edge of it (its like a map sensor connector toyota use) if you dont get the correct voltage test the wiring for breaks.
if that is OK then replace with good known sensor and perform reinitialization and retest. If same error occurs then the ECM is suspect or there is internal transmission damage.
