1995 Saturn SC-1 Overheats, Poor MPG

Sounds like a bad coolant temperature sender. These are known problems on saturns. Their composite plastic tips crack in time. When they crack they can leak which in turn ruin their wire connectior.

The ECTS (coolant temp sensor) has a very big impact on gas mileage, idle speed, air fuel ratio, and also is the input the computer uses to turn on the cooling fan. Saturn went to an all brass tip version in 2001 I think. Anyway get an updated version from saturn. Should be under $20.00. Try to reuse the wire connector. That little wire pigtail is over $30.00.

Good luck. Let us know what happens. :)

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.


NOTES:
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

Thanks alot Peppermrj my little red Saturn run alot better now has the horsepower it had before don't know about gas mileage yet but it is hard to think that little sensor had that much control over the whole car thanks again

Hope it works out well for you. Don't forget to double check that the cooling fan is coming on. Mine comes on when the gauge hits 3/4ths. It shuts off at around 5/8ths. I was suprised how long it took from a cold start to get hot enough to turn on the fan. On a ninety degree day I'd bet it took 20 minutes from a cold start till it came on.

That sensor tells the computer it is a cold engine when it fails. The computer stays in "open loop" and runs the engine with a very rich fuel mixture. The computer never gets the message that the engine is warm so you get poor performance, poor mileage, and more. Mine was so bad the idle would shoot up to over 2000 rpm whenever it felt like it. ?That was fun in traffic. :twisted:

Thank you so much Peppermrj the fan comes on about 3/4 of the way up and went off at about 1/2 way and it runs great now you are the man

my temp go to over half mark when sitting in traffic i turn heater on full and it helps from overheating also my rpm go up to about 3 and back down to 1 and then dies cked sensor has copper but the pig tail look coroded do i need the pig tial

[quote:75b706f4ea="edwin.vangundy"]my temp go to over half mark when sitting in traffic i turn heater on full and it helps from overheating also my rpm go up to about 3 and back down to 1 and then dies cked sensor has copper but the pig tail look coroded do i need the pig tial[/quote:75b706f4ea]

Ed, you need to make sure your cooling fan is coming on for certain and also if the pigtail is corroded replace it. The cooling fan should also come on when you turn the AC on.

Good luck and let us know. :)

[quote:e9691a2809="peppermrj"]Ed, you need to make sure your cooling fan is coming on for certain and also if the pigtail is corroded replace it. The cooling fan should also come on when you turn the AC on.

Good luck and let us know. :)[/quote:e9691a2809]ok i did the test with the jumpers gave me 3 codes po123 and po124 throttle pedal position senson/switch a circuit high input and switch a circuit intermittent the 3 code was po132 02 sensor circuit high voltae bank 1 sensor 1 it didnt change any of the censors but i did ck the connections on the po123 and po124 i didnt see any thing wrong with pig tails connections but cleaned anyway i didnt mess with the 02 sensor on exhaust left it alone went back to test again it light 12 3 times saying every thing ok so i cleared codes by disc. neg battery and reconnected and proceded with with the pcm learning ability to get the fuel system right it see to make a big diff.on everything but...................... not sometimes i will sit at stop light and rpm will rev. up to maybe 1 1/2then drop down almost stalling it does it a couple of time and then goes back to normal running at 1 rpm my fan does come on now that i did that test when sitting a stop i ck to see if running and it was i am thiniking i need to replace that cooling sensor and pig tale what do you think

I'm with you on replacing the ECTS and it's pigtail. Double check that you have no vacuum leaks also.

Good luck and let us know. :)

[quote:a3725bd834="edwin.vangundy"][quote:a3725bd834="peppeprmrj"]Ed, you need to make sure your cooling fan is coming on for certain and also if the pigtail is corroded replace it. The cooling fan should also come on when you turn the AC on.

Good luck and let us know. :)[/quote:a3725bd834]ok i did the test with the jumpers gave me 3 codes po123 and po124 throttle pedal position senson/switch a circuit high input and switch a circuit intermittent the 3 code was po132 02 sensor circuit high voltae bank 1 sensor 1 it didnt change any of the censors but i did ck the connections on the po123 and po124 i didnt see any thing wrong with pig tails connections but cleaned anyway i didnt mess with the 02 sensor on exhaust left it alone went back to test again it light 12 3 times saying every thing ok so i cleared codes by disc. neg battery and reconnected and proceded with with the pcm learning ability to get the fuel system right it see to make a big diff.on everything but...................... not sometimes i will sit at stop light and rpm will rev. up to maybe 1 1/2then drop down almost stalling it does it a couple of time and then goes back to normal running at 1 rpm my fan does come on now that i did that test when sitting a stop i ck to see if running and it was i am thiniking i need to replace that cooling sensor and pig tale what do you think[/quote:a3725bd834] my fan does work now if i sand the corroded pig tail will that make a diff. im one of those persons who want to try to make it work befor i have to spend 30 bucks on a plastic connector

I hear ya. Give it a try. If it is shot, you won't hurt it.

[quote:36621175cc="peppermrj"]I hear ya. Give it a try. If it is shot, you won't hurt it.[/quote:36621175cc] thanks for you help i will try the sanding of connector and if no diff i will repace it and the censor is there a way to ckeck the sensor to see if it is good??? and where do i ck for vacume leaks up by the air flow tube and the seal that the pcp valve goes into and maybe some vacumes lines by the throttle body ????? or whatever that thing is called once again thanks peppermrj

There is a test procedure for the ECTS. I will e-mail it to you. Check the PCV hose and the power brake booster hose. See if they are cracked and brittle or soft and gummy. Make sure the throttle body is tight. You can spray starting fluid (use caution fire hazard) around the intake manifold or use a length of tubing held up to your ear to listen for a leak.

[quote:246ff5bd44="peppermrj"]There is a test procedure for the ECTS. I will e-mail it to you. Check the PCV hose and the power brake booster hose. See if they are cracked and brittle or soft and gummy. Make sure the throttle body is tight. You can spray starting fluid (use caution fire hazard) around the intake manifold or use a length of tubing held up to your ear to listen for a leak.[/quote:246ff5bd44] ok i will ck those things in the morning im hope i dont have to bother you again but im sure is will i think its great you can answer everyones questions and help up out like you do have good night