So while I was replacing my cooling fan motor I realized that the sensor that plugs into the bottom of the coolant reservoir was unplugged, so I plugged it back in and finished up the job. After putting it back together; I started up the engine, went to the engine bay and pulled the ECT sensor. After a few seconds the fan kicked on. While all of this was happening there was no lights on on my dash at all. THen This morning when I went to go to work the CEL and the Low Coolant light are on. There doesn't appear to be any effects performance wise; however it is troubling to see. Is it because I pulled the ECT while the vehicle was runing? Maybe the sensor I plugged back in... I don't know.
Me: Mmmmmm, what is this? It tastes just like chicken and rice!
Him: Hey! That's my Civic bro!
Me: Sweet, I was right.
but the low coolant sensor was never plugged in before, and you never had a light on the dash? i would test the voltage of the plug, make sure its getting power and a wire isnt crimped/defective somewhere as it was unplugged and dangling or damaged some how. thats odd it came on after being plugged in.
as far as the other CEL, did you use a scanner to see what code its pulling? (free at almost all auto parts stores if you dont have a scanner)
erase the code if its related and see if it comes back. it could be a residual signal from being unplugged perhaps. also, if you have the money hit up Amazon and buy an OBDII scanner. it'll pay for itself with the first use..as shops will easily charge $120+ to plug one in and tell you exactly what you can find out with your own scanner
04 Cav. 2dr. 5spd. My DD. 'Nuff said.
So the CEL has turned itself off, however the low coolant light is still on. The coolant is topped off so I am thinking it is that sensor I found unplugged.
Me: Mmmmmm, what is this? It tastes just like chicken and rice!
Him: Hey! That's my Civic bro!
Me: Sweet, I was right.
I went out and tapped on that thing pretty hard and the light is still on; however, I noticed that when I unplug it the light goes off, plug it back in the light comes on. Pretty sure the sensor is just bad.
SweetnessGT wrote:The low coolant light is an easy one. Take a screwdriver and tap the bottle near the sensor while the car is running.
It will turn off... 
One of the oddest little "idiosyncrasies" of a J-body but any time you empty that expansion tank and refill it with coolant you need to tap the sensor to tell it to shut off.
The check engine light turned off because you unplugged the ECT temporarily which freaked the engine right the eff out - the pcm uses it for a lot of functions. The light went off after a few cycles seeing that the sensor was in fact giving a reading.
-Chris-
Me: Mmmmmm, what is this? It tastes just like chicken and rice!
Him: Hey! That's my Civic bro!
Me: Sweet, I was right.
