Wiring experts, your help is needed. Thanks

I noticed this connector and wire on the drivers side after the car had some work done recently, a shop installed new valve cover gaskets.

The loom comes through the motor mount on the driver side.

Never noticed it before, but I tied it up with a zip tie for now.

Single wire blade connector green in color.

88 Firebird Formula 305 TBI with open air cleaner mod.

 

Somewhere in the area of the two sparkplugs there should be a temperature sender(or switch) screwed into the head that the mystery wire is supposed to be connected to .

 

Precisely what he said:

Temp gauge sending unit.

Between #1 & #3 spark plugs.

 

The passenger side head has the radiator fan switch to kick the fan on at 215 or so which I just replaced recently.

In the 1st picture up on top on the intake manifold by the thermostat is a sensor (2 wire yellow/black connector) that I thought is for the coolant temp sender for the dash gauge?

 

The black/yellow one is for the ECM .

Rather than rely on one sender to tell the ECM , and then the ECM tell the gauge as most folks think it does , on our cars there is a temp sender/switch for each function .

One for the ECM , a second for the radiator fan (which is also controlled by the ECM*) and a third for the dashboard gauge . If you had a TPI with a separate "cold start injector" then there would have been a fourth one for that . A final fifth (or fourth in your case) would be the "IAT" (Intake Air Temperature) sender mounted somewhere in the air induction system .

* The radiator fan can run from either it's own temperature sender(switch) or from the ECM sending it a signal just in the same way as the fuel pump can run from it's oil pressure sender(switch) or from the signal the ECM sends it .

bet ya didn't think you had that many temperature measuring devices kicking around under the hood , huh ?

 

^^^ Thank you Sir!, it makes more sense now.

Also explains why my Temp Gauge has stopped working on the dash cluster!

 

Cars have had temp gauges since long before ECUs.

A clue is, the temp gauge wire has that old old old style connector, whereas the CTS has the computer style.