Coolant sensor craziness!
 

Alrighty guys, this is probably the craziest thing my car has ever done. Today, I finally got rid of my stock exhaust system on my car to help my turbo breathe a little easier. In doing this, I cut the wires to the rear O2 sensor as i couldn't find the actual plug for the darn thing, but no big deal, I can always solder them back together for whatever reason.

Anyways..... I'm running an open DP for the moment and went out for a drive. For whatever reason, as soon as I get into boost, my stock dash coolant gauge increases as boost increases. It literally pegs out to the other side under WOT and will go so far that it will instantly reset itself back to where it started. As soon as I let off the throttle from being in boost, it then goes back to normal reading again.

In other words, my coolant gauge has gone nuts on my dash. I haven't really looked into anything yet, will do that tomorrow. Megasquirt is wired in parallel with my stock ECU and they both share the stock coolant sensor and have been for the past 8 months without issue, until now. I haven't hooked up my laptop to check if it actually reads crazy or not in MegaTune, but what would cause something like this to happen?

All help or comments is appreciated! Thanks!

Plug in a laptop and see if the coolant temps are really going up. If they are I would suggest staying out of boost. I have no clue why they are going up like that though.

**UPDATE**

I hooked my laptop up and Megasquirt is reading completely normal, so its just the dash gauge itself going crazy. Anyone know where I should start checking to see why its doing this?

The coolant sensor is on the back of the head, I'd start there.

There are two sensors. One for the engine and one for the gauge itself. I would check your other grounds to make sure something didn't come loose at the same time as the O2 sensor removal.

So the coolant sensor on the back of the head is the one the gauge reads from? I'll take a look there when I get a chance I guess.