Hello guys, got the p1780 code , cleared it and it appeared again i changed the pnp switch after 3 hours of trying😭, still the same issue , car is Gs400 2000 , symptoms are: no reverse light , pwr switch not working , poor shifting

PS: i have the gs430 SHIFTER AND Bezel from the last owner i dont know why he changed it , it could be the problem?

 

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Well, quick google says P1780 is "Park/Neutral Position Switch Malfunction", also possible relation to ECM getting signals for two gears (such as N and D). You're going to have to start from the PNP, then work your way back through the circuit.

Do zero or two gear positions light up, in the dash, while shifting?

Yet it appears that there's some level of adjustability with the PNP switch (looks like an alternator, with an adjustment bolt, and a setting bolt), so if you replaced it with new, guessing it needs to be adjusted so that it recognizes only one gear. You might have to release the bolts some, put the car in to gear, then adjust the PNP switch back and forth, until all gears indicate only one gear selected.

This can effect everything, if it's off... lights, shifting, etc. Even seen on some minivans with power sliding doors, that they stopped working, when the door controller didn't know the minivan was in P.