Toyota Repair: Toyota Rav4 error code P1780, toyota rav4, position switch

Question
We bought a used 1996 Rav4--automatic transmission, 100,000 miles.  The check engine light was on.  The previous owner said the light had been on for quite some time and she thought it was an O2 sensor.  I took the Rav to AutoZone and they ran a scan and gave me the code P1780 which they said was the transmission control switch.  My question is---is this something that needs to be replaced?  What happens if you do/don't replace it.  Is it expensive to replace?  Thanks

Answer
This code is related to a malfunction with the park neutral position switch, it's located on the transmission near the radiator directly behind the shift selector lever, it has a large connector with a lot of wires, at times the connectors can get corrosion on the inside, try removing the connector and check for any corrosion and clean the connectors on both the switch and the wire harness side, if that is not the case the switch should be replaced.