Question

What is code PNP P1780 on a 1998 Toyota Camry 2.2L?

Answer 1

The park/neutral position switch goes on when the shift lever is in the N or P shift position. When it goes on terminal NSW of the ECM is grounded to body ground via the starter relay thus the terminal NSW voltage becomes 0V. When the shift lever is in the D, 2, L, or R position, the park/neutral position switch goes oft, so the voltage of ECM. Terminal NSW becomes battery positive voltage, the voltage of the ECM internal power source.
If the shift lever is moved from the N position to the D position, this signal is used for air-fuel ratio correction and for idle speed control (estimated control), etc.

Basically this is the neutral safety switch. The car won't start if the switch has failed or it's out of adjustment.

Answer 2

P1780 Toyota Code - Park/Neutral Position Switch Malfunction
Read more: https://www.autocodes.com/p1780_toyota.html