Mystery Sensor / Switch

[holmanrd]

Hello Gents,
I have a mystery sensor or switch in my cylinder head. Drivers side hidden behind the fuel filter canister. it is not plugged in and I can't find the harness side for it.

It's not the Coolant Temp Sensor. It's in the back of the head and plugged in.
It's not the Air Temp Sensor. It's installed into the intake plate. Not plugged in because my EGR fell off and I can't find it.

I have been searching for hours and can not find the answer.

One possibility I read was an Engine Coolant Thermal Switch (auto trans) but I can't find the wire harness end to plug into it to confirm.

It's for a 97, w/auto trans, used to be an EGR truck.

Any ideas?
Anyone with a like truck tell if they have the same sensor and where the harness plug leads?

Any help is appreciated, Thank you.

 

[BigPapa]

Only things I can think of is someone’s moved the Oil Pressure Sensor, installed another one for some reason, or maybe put an Oil Temp Sensor there. There are three or four ports along the oil galley there.

 

[holmanrd]

The oil pressure sender is still in the original spot in the front and hooked up.

This sender or switch if definitely in the head only options are air or water.

This has me scratching my head.

 

[BillBaker]

A picture would be nice to see this mystery...

 

[GAmes]

It is the coolant sensor for the EGR, about the #4 cylinder position. Page 25-27 in you factory service manual.

 

[holmanrd]

BillBaker, I will try again.

It is stuffed so far up in there with so much around it, my pic was just awful.

It is so tight up against the bottom of the head, the head is actually dished out for clearance.

I will try to get some better lighting up in there or rip off my filter canister to get a straight view in there.

 

[holmanrd]

GAmes, I think you hit the nail. It's not hooked up because my EGR came up missing about 10 years ago.

Dang it I read through the manual a dozen times last night looking.

I need you on permanent retainer for tech (and my stupidity) reminders. Where do I send the retainer check?

 

[GAmes]

I work for beer. One of these days we might meet.

 

[holmanrd]

It would be my pleasure sir.