When I replaced mine I did so with these instructions from the very talented Wolfman.
"The ECTS is a two wire sensor used by the PCM to measure engine temperature and set engine/transaxle operating parameters accordingly. On 91'-95' SOHC and DOHC engine equiped "S" series Saturns, there is a SEPERATE sensor used for the gauge. On these cars, the ECTS is the TWO WIRE sensor located just below where the upper radiator hose attaches to the engine. (The other ONE WIRE sensor nearby is used for the gauge) On 96'-02' SOHC and DOHC engine equiped "S" series Saturns, the ECTS is in the same location, but also operates the temperature gauge. (The other one wire sensor is deleted)
To change the ECTS in either case you'll need:
13mm DEEP WELL socket (6 point variety recomended)
and a socket wrench.
Perhaps a pair of needle nose pliers
Obtain the "NEW style" all brass ECTS from SATURN, it will come ready to install with nothing else needed.
DO THIS ONLY ON A COLD ENGINE!
Proceed as follows:
Remove the air snorkle running from the front of the car to the throttle body. (Or air filter housing on 91'-94' SOHC)
Locate the ECTS as described above, the electrical connector is held on by a plastic connector with two little "ears" on it that grip the lip of the ECTS. It can be hard to see. To remove the connector, SQUEEZE the plastic hood about 3/8 in. BELOW WHERE THE WIRES GO IN with either your fingers or needle nose pliers and GENTLY pull away from the engine. DO NOT PULL ON THE WIRES! If the connector does not easily release, reposition your fingers (or the pliers) and squeeze/pull again. Eventually you will find that "magic spot" and the connector will come off quite easily.
Inspect the inner portion of the connector for any signs of corrosion. If corroded, it should be REPLACED (Available from Saturn) but cleaning it can sometimes do the trick.
Remove the coolant resevoir tank cap to relieve any pressure in the system, then put it back on TIGHTLY to avoid excess coolant loss when the sensor is removed.
HAVE THE NEW SENSOR READILY AVAILABLE BEFORE THIS STEP!
Using your 13mm deep well socket, remove the old ECTS from the engine by turning it counter clockwise. Keep the socket as straight as possible over the sensor. (When it comes free from the block, some coolant will spill out, DON'T PANIC)
Quickly thread the new ECTS into the hole BY HAND to minimise coolant loss and prevent crossthreading.
Using the 13mm deep well socket, tighten the new ECTS into the engine by turning it clockwise. Keep the socket as straight as possible over the sensor to avoid damaging it. Keep turning until you feel it "bottom" in the hole but DO NOT OVERTIGHTEN IT!
You reconnect the electrical connector by placing it over the end of the new sensor and then GENTLY pushing in on it while SLOWLY rotating the connector. When everything lines up, it will then just pop into place.
Reinstall the air snorkle.
Coolant loss will be minimal but messy. You should NOT need to top up the coolant as less than an once or so will leak out. You "can" rinse off or mop up the spilled coolant if you wish (recommended) Keep PETS AWAY some (green) antifreeze is POISONOUS to them but tastes "sweet".
You "should" reset the PCM after changing this (or ANY sensor) this does NOT require any special tools, just disconnect the NEG battery cable for about 15 secs.
When remeoving the electrical connection from the sensor, TRY using your fingers FIRST (a little contortionary talent helps) use pliers as a "last choice"
DO THIS ONLY ON A COLD ENGINE!"
Patience and a liitle elbow grease got me a better running Saturn. :P
Wednesday, March 1st, 2006 AT 1:20 PM