I've had this gauge for a while and it has always worked flawlessly.
Picked up the truck from the shop a few Friday's ago and it was dark by the time I left the shop so I didn't notice the issue that I'm about to describe.
That Sunday I went to leave the house in the truck and noticed that the gauge didn't power up. I thought that it was simply unplugged from the OBD2 port from when I had plugged up my code reader a couple of nights prior. Nope...it was plugged in. I unplugged it and replugged it several times...nada.
It began raining as I drove into town and I turned on my wipers but noticed that the headlights hadn't turned on automatically. I turned them on manually...scratching my head as to why they had not turned on...when I noticed out of the corner of my eye that the scan gauge was now ON!
I turned the lights off... gauge powered off...lights on...gauge on...parking lights on...gauge on...lights off...gauge off.
The gauge powers itself thru the OBD2 port...I'm lost. Guy at the shop is puzzled as well.
Any thoughts or guesses?
Thanks!

 

I am puzzled as well. What was it in the shop for? What all did they do/mess with?

 

THIS particular time...installed Assassin Bars and new dual in-line fuel pump set-up...
Just in case anyone wonders...I had scanned the DTC's on Friday night cuz the light was on...temp sensor was unplugged.

 

Cig lighter fuse blown?

 

The one I was charging my phone on wasn't.

 

The one on the far right is on its own fuse, and that is what powers up the DLC connector. The other 2 outlets are on a seperate fuse.

 

Good info...I didn't know that...BUT...How could the headlight switch override a blown fuse?

 

Honestly, I don't have any idea, unless you've got something aftermarket wired in that's causing a backfeed when the lights are on.

 

I doubt this is it but when mine didn't turn on when I started the truck it was because the alternator was going out. It was the weirdest thing, I would drive around and eventually it would kick on by itself or I could turn it on manually with the button and it stayed on. When I replaced it, everything started to work just like it should when you hit the key.


Just an idea, might not be it but that's what I thought of.

 

Funny thing you say that...
While @ the shop...after this was noticed...and trying to get the new HD tensioner indexed correctly...my alternator took a dump...pukin' $#!+ out the cooling vents...
new alternator is now on and we should be firing her up this week once the fuel supply and return lines are completed...
IF that's it...I still wonder how the headlight switch came into play.