which plug or sensor is this?

[dookz4x4]

hey everyone i have a 99 tahoe 5.7 engine so i have replaced alot of parts and have done alot of work, im looking to change out the sensors and i cant seem to figure this one out... okay on the right side of the engine, drivers side from looking or standing at the truck, right above the spark plugs there is a looks to be 02 sensor/spark plug i cant seem to find anything online about wat part it may be, mine looks old rusted and in bad shape, it has 1 wire to a blue/black connecter... if anyone ever changed or knows wat this is i appreciate a responce ahead of time

 

[Slammed]

Sounds like a temp sensor

 

[lesterl]

Dash guage temp sensor, PCM sensor will be next to water neck.....

 

[Slammed]

Oil pressure?

 

[lesterl]

Oil pressure sensor is in back by distributor and has 3 wires.......

 

[Slammed]

Ok take a picture and post it

 

[lesterl]

Drivers side of engine, just above spark plug level, but below the rocker arm covers near and just above #3 plug (IIRC) is only one sensor, short 1 wire sensor. It is the temp sensor for the dash guage, dont believe unplug it and the gauge will quit. Plug it back in and voila guage works.