ok so ever since i got the car my service eng. light has been on. for the last week or two there has been a little bit of a promblem when i drive her. when the temp would get up to about 120 it would start stumbling on it self jerking back and forth when i was driving it or if it was just sitting there idleing it would raise and drop the rpm on its own until it would reach about 220. so today i went to go put it on the computer and the dang thing was not reading it. so i decided to jump the computer useing a paperclip so that it would read off the dash. well it came up to be a code 15 which in my book tells be that it is a temp senser of some sort. so here is my question and quest to fix the promblem. what would be the more promblamtic (sp) senser to be doing that to my dear beloved car. any and all info would be real great thanks

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long days and short term memory don't go togther very well

by the way it is a 2.8. that and it doesnt seem to be overheating. the fan will kick on right on if it gets 1 to 2 bars above the 220 mark. but that could just be the guage cause the needle did come off at one time and we rest it to as close a posible. usaly it will stay right belowe 220 after it goes thrue its little fits unless i sit in traffic for a peroid of time then it will go just above 220 then it will drop back down. the fan switch is the 220 on but the thermostate is 180.

Here is the procedure for finding the codes and what they mean. You probably just have a bad coolant temperature sensor.
https://www.fiero.nl/cgi-bin/main.cgi?ECMCodes and yes your temperature gauge can be off if the needle fell off. The roaming idle could be caused by the IAC valve. Maybe yours just needs to have the pintle and seat cleaned so it will seal better.

[This message has been edited by avengador1 (edited 01-28-2008).]

The code 15 for coolant temp sensor is the one for the ECM, not the gauge temp sensor or the fan switch (another temp sensor). We have all kinds of different sensors to go bad! The one you are looking for is located below the thermostat housing in the lower intake manifold. I'll post a pic. The test is to place an ohmmeter or multimeter set to ohms on the 2 little pins and read the resistance. You do this when the engine is cold and you know the exact outside air temp (place a thermometer on the engine overnight). You will probably need to remove it for this test as it's hard to see much less get the multimeter probes on those 2 little pins.
Here is the ECM coolant temp sensor on a lower intake manifold (plus the cold start temp sensor and fan switch (temp sensor):

This is installed in the car:

Removed from the lower intake (it is screwed into an adapter on our engines)

Sensor resistance table vs temp:

quote Originally posted by Hudini: The code 15 for coolant temp sensor is the one for the ECM, not the gauge temp sensor or the fan switch (another temp sensor). We have all kinds of different sensors to go bad! The one you are looking for is located below the thermostat housing in the lower intake manifold. I'll post a pic. The test is to place an ohmmeter or multimeter set to ohms on the 2 little pins and read the resistance. You do this when the engine is cold and you know the exact outside air temp (place a thermometer on the engine overnight). You will probably need to remove it for this test as it's hard to see much less get the multimeter probes on those 2 little pins. Here is the ECM coolant temp sensor on a lower intake manifold (plus the cold start temp sensor and fan switch (temp sensor): This is installed in the car: Removed from the lower intake (it is screwed into an adapter on our engines) Sensor resistance table vs temp:

i know this is going to sound stupid but anyways. will i have to drain the antifreeze when i take this one out. and when you say remove it to test it is that just removeing it from the intake or remove the intake to get to it easer.

You remove the sensor for ease of access, it is not required though. Since you will lose a bit of coolant it would be better and faster to test it right on the car. You don't remove the lower intake. If you decide to remove the sensor, just drain enough coolant to get the level below the sensor. There is not too much coolant in that area. The bulk of the coolant would be in the block, tubes, and front radiator.

The 2 pins are quite small. (sensor on the left)

[This message has been edited by Hudini (edited 01-29-2008).]

ok i think i figured out the promblem. but i still get the code once it has ran for a little while. but i think i know what it is. the plug for the ecm temp sensor was a bit corroded and it is also cracked. so i am pretty sure that is what the promblem is. (crossing fingers and toes and what ever other body parts). and yes i have unhooked the battery for 20min just to make sure. so with it being loose and crack it just is not getting the right conction. figure i would put that down so Hudini would be happy. jk but thanks you all.

lol, and I appreciate it. Too many threads die without a conclusion. There is so much to be learned here it's just nice when someone posts what their fix was so the rest of us can benefit.