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(2000 Toyota Camry)
in Mohegan Lake, NY on April 19, 2009
ABout 86000 miles on the car, get a P1780 failure code. I know what the code means, and have seen a few potential problem in forums online. Whats the easiest/cheapest way to figure out what actually needs to be replaced or fixed?
Displaying 2 answers & 4 comments
Popular Answer
The code refers to a park/neutral safety switch malfunction. It may indeed be a "bad" neutral safety switch but check for a break in the wires in the wiring harness on the left trunk lid hinge 9peal apart the harness and inspect it closely, repair any damaged wires there.
on August 08, 2010
I had exactly the same problem. Also had problem with the backup lights and also the Reverse indicator on the dash would light when pressing the brake pedal even though the gear selector wasn't in reverse. The break in the wires was found about three inches before the wire bundle coming down the left hinge joined a larger wire bundle in the rear quarter panel.
on October 18, 2010
Thanks a million for your tip I had the same exact problem and sure enough there were three broken wires in the area cited in this report.

John Chrisney
on October 23, 2010
2000 Camry - Noticed the license plate lights weren't working. Found 3 broken wires and 4 frayed wires at the left trunk hinge location. Clearly this is a problem spot as the wires must flex substantially here. It also appears that the wire bundle "saws" itself on the trim panel edge. I repaired them by adding about 3 inches of additional "loop". I also trimmed the top edge of the panel so as to not rub/saw it's way through the bundle. The check engine light & code P1780 is now off as a result.
on December 08, 2010
Same as Anonymous, October 23, 2010, 08:25.
Another web has a Toyota tech saying that the harness is 99% the cause for P1780. codes.
on August 04, 2017
Thanks so much for the great info ... who in the world would have ever guessed the problem would be caused by a wire in the TRUNK ...!!
Thanks again -- you saved me multi-hundreds of dollars!!
I found the broken (white) wire, soldered in a new piece and all it cost me was $7 for a spool of wire (of which I used 6 inches!!)
The break was about 3 inches from where the smaller bundle that's tied to the hinge joins the larger harness -- a little tough to get at but not impossible.
Many, many thanks !!
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