Have a 1994 saturn sl i changed out both temp sensor with some that i had out of a nother saturn b/c fan would not come on when car got hot but would come on with a/c on. And now i still have same problem and now i am geting a check engine light.and the code on that is a code 49 idle rpm out of limt high (vacuum leak) why would this be?

 

Well, a vacuum leak could cause higher than normal idle RPM, but changing out the Engine Coolant Temp Sensor (ECTS) normally won't cause that. There are other possibilities to consider --> Throttle Position Sensor (TPS) could be misadjusted, or either the Manifold Absolute Pressure (MAP) sensor, Mass Air/Flow (MAF), Inlet Air Temperature (IAT) sensor could be at fault.

By the way, if your temperature gauge was operating normally, you didn't need to change that sensor. Since the fan operates when the A/C is on, I would suspect the Body Control Module (BCM) as not sending the right control signals to the fan -- although since you are using a "scavanged" sensor, I'd check the resistance reading on the sensor as a first step.....

 

thanks for the reply i got the vacuum leak it was a hose go from the intake to value cover.i but a new sensor in today and still the fan well not run when up to temp but what i did find out was if i take a tester and test for power with tester on ground at battery and then test yellow wire it well turn fan on and i test ground wire and i am good there what can i do next thanks

 

pls define "car getting hot". Fan will not kick in until temp gauge gets up to 3/4 tick on s cars. You've tested that the fan motor is good and that the fan relay is good (since it actuates when the PCM sends a signal when you turn on the A/C).

You have not determined if the temp sensors are good. The single wire is for the dash gauge; the 2 wire is the ECTS for the temp measurement that goes to the PCM.
Old style resin tipped ECTS are prone to failure so the one you swapped in, if not a brass style replacement, is likely crap

So I recommend

1) replacing the ECTS (two wire temp sensor)

It is also possible that the engine is not getting hot enough to kick the fan in.

After replacement let it get up tp the 3/4 tick or a little past on the gauge and see if the fan kicks in. If not then we'll track it down from there

 

i have replace two wire sensor(new) and fan still well not run and car well get hot all the way to red. help

 

When you replaced the two-wire sensor, did you also replace the electrical connector that hooks the sensor up ??

 

yes i did put a new connector on it and still fan dont run and car well run hot..so i just went for lunch and the temp light come on as well as the check engine light and then the fan went on and car was only showing half way point on temp.so i got the code and it was code#14? so now what should i do thanks so much

 

code 14: coolant sensor high resistance or shorted

since the resistance of this device is high when cold and low when hot, and you just replaced the sensor and the connector (we'll assume them to be the right GM sourced parts) seems to me:

1)the sensor you bought is a dud
or
2) The sensor is fine but the wiring between the sensor and the PCM is not --there is a poor connection between the two. This would cause the overall resistance of the circuit to be high, which equates to the PCM sensing a low coolant temp and thus not turning on the fan at the proper coolant temp. Check your wiring to ensure the new connector is firmly spliced in. Check the voltage across the two connector sockets -- you should see 5V DC.

If you don't, then you know the issue is in the wiring between the sensor and the PCM. Could be a bad connection/no connection (coolant sensor high resistance) or the +5V wire could be shorted to ground somewhere (coolant sensor shorted)

 

should i check it on the plug or at the splice runing and up to temp?now when i start my car it is runing poor at first then ok after a 5 min run but lights are still on.(temp and engine and fan)going see what voltage across the two connector sockets is then ill post thanks for all the help..i read the code again and now i have code 14 and15.temp high and low? and when i fist start car it idles up and then down and car will die. if i take off in car it will start chuging but is fine after car starts to get warm.if i unplug 2 wire sensor and just plug old sensor in and just have it laying there (not screwed into block) car runs fine but still have all lights.could thermoastat have any thang to do with this?

 

check sensor like derf said to do and end up geting me a bad sensor put in a nother sensor and car seems to be doing fine as of now thanks for all the help..