could someone post a picture of where the coolant temp sensor is on an 02 impreza 2.5? I've been searching all over and all of the descriptions dont seem to make sense to me and I can't find anything that looks like the pictures of the sensor itself. I took off the alternator thinking it was under there and thought I found it right next to the crankshaft position sensor but it wasn't it. What was it?

this is an 03 - maybe the same;

 

The sensor under the alternator is the oil pressure switch.

 

Coolant temp sensor is on the coolant crossover pipe under the intake manifold. Under the number 3 intake runner (passenger side) it's gonna be under and to the left of the large wire harness loom. There may be some hoses and wires in the way.

 

There are two sensors there. One is for the gauge or light in the instrument cluster, this one has one wire. The other is for the ECU and has at least two wires.

Hehe finally found it! thanks guys. It turns out it was unplugged. Thats what happens when you tear your engine apart and don't get it all put back for about a month- things get forgotten. Still not quite running right, but it sounds almost normal now except that its idling at about 1700 and after about 5min it starts backfiring. No CEL yet, though

The sensor under the alternator is the oil pressure switch.

 

Coolant temp sensor is on the coolant crossover pipe under the intake manifold. Under the number 3 intake runner (passenger side) it's gonna be under and to the left of the large wire harness loom. There may be some hoses and wires in the way.

 

There are two sensors there. One is for the gauge or light in the instrument cluster, this one has one wire. The other is for the ECU and has at least two wires.

 

When they are this new its 1 sensor that does both.