1999 Ford ranger help

Trying to figure out what this connector goes to. Any guesses.

This thing has sat for so long I've forgotten and I did not identify it properlywhen pulling the motor 

Thanks

Which engine/trans? Where on the harness is that? It looks like maybe that's near the firewall on the driver's side?

Single wire, right?   Maybe a knock sensor?  

Sorry guys. 3.0 v6 auto. That wire is near the firewall on the passenger side. Not sure about single wire. May be single or two wire. 

Does it use 1 wire oxygen sensors?

In reply to BrokenYugo :

O2 sensor is the blue one in the pic. 

Besides knock I'm not sure what else would be 1 wire on a 1999, oil pressure switch? Some temp sending units are one wire, is engine coolant temp already hooked up?

I don't know. I'm at a loss. Literally can't find a single place this would plug into .

You could just start it and see what code it throws, they'll usually run ok (open loop only) with one or two unplugged.

went back to it and dug deeper. Single wire and it hangs right at this threaded hole. Would a knock sensor be placed there on the block? Notice it's right near where the block bolts to the tranny. 

Hmm.... is this old enough to have a SPOUT connector?

It does look really familiar.  Wonder if it is the ground that Ford likes to put on one of the valve cover bolts.

It's been awhile since I've been near that part of my 3.0, but I think that's the oil pressure sensor location behind the passenger cylinder head.

Cylinder head temperature sensor maybe?  Ford likes CHTs rather than coolant temp sensors.  (They don't care how hot the coolant is, they care how hot the metal is, since that is what really affects combustion)

Thanks guys. I'll do a little research and hopefully figure it out. 

Bringing this back up from the dead. I've git everything hooked up on my ranger (really a b3000 mazda) and car wont crank at all. Either the battery is dead as a door nail or I've failed to connect a ground wire or something. Would a loose ground wire or one not hooked up keep the engine from cranking?

Im at a loss really. Not familiar with these trucks at all.

Thanks

The ignition module ground is a separate 1 wire connector, goes to a little thingus that bolts to a valve cover stud on the right valve cover.

Strictly by recollection, here, and mainly having worked on this engine in Tauruses.