P1780 issue with a “special” twist
 

I have the P1780 Neutral safety switch issue, but with a “special” twist. The check engine light came on the other day and my HVAC controls decided to change from Fahrenheit to Celsius! I had one hell of a vibration from a universal joint that was about to crap the bed and I believe that the vibration might have added to the issue. I had overlooked the universal because my upper control arms were failing and they had in turn caused my tie rod ends to prematurely wear which caused the front end to vibrate like crazy. All of this happened as I am working Nights and a lot of 12 hour shifts so I’m not exactly on my game at the moment. But..wait..it gets better! Now my truck won’t shift but once. I can move the shifter into any gear and the HVAC display stays in Celsius except for 1st gear where it changes back to Fahrenheit.

I bought another neutral safety switch, but after reading up on the issue I don’t believe that this will solve anything because the truck starts and runs fine. I changed the universal so the vibration is gone except for the front end wiggle which I will repair after I get it to shift again.

I also noticed yesterday as I played with the shifter that the instrument cluster is starting to glitch out with the gear indicator on the dash. I was contemplating changing the printed circuit board.

I apologize for the long ramble.

If anyone has any comments or suggestions I would be very grateful!

Bump

Anyone?

Intermittent grounds can cause a whole range of seemingly unrelated
problems.

Thank you for the input. I will start checking.

Sent from my SM-N950U using Tapatalk

I had the exact same issue on my 4Runner ('99 Limited A/T). After a lot (A LOT) of troubleshooting and reading online, I narrowed it down to the Instrument Panel Circuit Board (Part 83861-3D260). It's the blue "sheet" that sits behind the gauges (2:40 in the video). Turns out after twenty years and 300k miles, some contacts wore loose or something, I don't know. Anyway, I replaced that and voila, it solved all those problems! Here's a video from Timmy the Toolman that should help you remove the guages. And another VERY helpful link from smallfry from the T4R forum. Good luck!

YouTube

Transmission Issue????



Sent from my Pixel 3 XL using Tapatalk

@SusVir
I changed out the circuit board last night and it fixed the problem. Thank you very much.