This plug comes from a tube going in front of the battery...



I can't figure out what it plugs in to.

 

Low coolant sensor. It's on the radiator below the cap.

 

Thanks a lot! No lights on the dash came on, I found this by chance.

Should my SES light have come on?

 

No. The low coolant level sensor is only connected to the "low coolant" light on the dash (and to the BCM for a "latching" feature). If you unplug the harness connector, the dash light stays off. It is not connected to the PCM and will not result in an SES light.

There's a good chance the low coolant sensor is dirty or corroded, and is causing the "low coolant" light to stay on, so someone unplugged the sensor to turn the light off.

From Shoebox:

http://shbox.com/1/low_coolant.jpg

http://shbox.com/1/4th_gen_tech2.html#low_coolant_lamp

http://shbox.com/1/low_coolant2.jpg

 

Nah im pretty sure when i got a new water pump they never plugged this back in. I talked to the previous owner and he said he never unplugged it.

No light comes on with it in, either.

 

Yet. Sometimes the response is intermittent....

 

Yeah the light randomly came on after I drove it yesterday while it was plugged it. The coolant level is fine, so I'm guessing the sensor or wire is shot. The light stayed off all day today though....

 

It's most likely the sensor. Just drain the coolant below the sensor level and swap it out with a new one. Don't bother trying to clean it and all that nonsense. Been there, done that, didn't work. Best to get a new one.