Cooling Fans Issue

[Talonman86096]

Ok really long story but I am having problems with my cooling fans not turning on in my 96 Eagle Talon TSI FWD. A while back I had a new temp. sensor put in which corrected a problem but i think lead to this one. For some reason there is a ground wire from the temp. sensor to the negative termanial of the battery. And now for some reason my cooling fans will not turn on by themselves, if i turn the A/C on they will come on and turn off just like they should on their own. If you disconnect the ground wire from the battery the car will not idle right and just run like crap and the check engine light will come on and the cooling fans will run all the time and not turn off. Ive had it to 3 or 4 different shops and no one can figuare this out i am completly stuck and have no idea what is wrong. Also it idles to high and the gas seems to burn extra rich idk how to correct that problem either. I know there is an idle screw somewhere but i havnt located it yet. If ne one has had a similar problem to this or has any ideas of what could be wrong i would appreciate it. I just had a brand new Big T28 turbo and 3" turbo back exhaust put on but this problem had occured way b4 this and is the only thing wrong with the car and its driving me nuts. Ne help will be greatly appreciated. Thanks

 

[luv2rallye]

I assume you're talking about the 2 wire engine coolant temp sensor (black and black/white wires). Your problem is that black wire should not be going to the battery negative. It should be going to ECU pin 92 which is an ECU signal ground for sensors (which is either isolated from battery ground or the signal return must come here first before going to battery ground in order to always have correct voltage readings at the ECU). Many of the other engine sensors also use this wire as their ECU signal ground (eg. O2, throttle position, air flow, MDP, etc) so it is not surprising other things are being affected also. Vfaq/Vfaqlocator incorrectly identifies 2g ECU pin 92 as "Ignition switch" instead of "signal ground" which may also have confused the issue. The harness wire was probably missing or broken off so he had to decide where to connect it. Since he knew it was a ground he chose the battery negative not seeing any other wire there. I was wondering how long it would be before someone did this.

 

[Talonman86096]

Ok so i looked into that just to see where the wires were running and it looks like out of the harness there are the two wires the black and the black/white and it appears that they run back to the computer or somewhere like they were orginally but i cant be sure of that because i cant follow them the whole way and dont have the equipment to get a good look at it. But it appears that this red wire is just an added thing for some reason and it goes right to the battery. Its like he had to add it to make the car run correctly. I dont know if maybe its just an add extension to the black wire cause it wasnt long enough or something cause like i said i cant get a real good look at it. Is it possible that he had the black wire connected to the wrong pin on the computer and to correct it he had to add a ground wire??? Im going to give your response to my mechanic and go from there and see what we can find. Thanks for the help your really the first person who could shed any kind of light on this situation. thanks

 

[luv2rallye]

Have your mechanic or you unplug the sensor, disconnect this suspicious wire from the sensor plug to battery negative, disconnect battery (to protect ECU when unplugged), unplug the ECU, and then measure continuity (ohmmeter) from the sensor harness black wire to ECU harness plug pin 92. It should be 0 ohms. If not, that's your problem (and probably why someone added that wire). Then measure from ECU harness plug pin 92 (again with it unplugged) to the battery negative cable (or body ground). There should be no continuity. If there is, then the black wire is grounded somewhere before it reaches the ECU which it should not be.

Here is ECU pinout: http://www.vfaq.com/mods/ecu-harness-2G.html

 

[Talonman86096]

Ok so its been awhile since ive put up any updates to my problem. Everything that was said above was done and checked by my mechanic and everything turned out fine so I am really stuck once again. I have no where to start from once again and its really just getting irratating haha. If any one or the person above have any other ideas as to what could be the problem I would really really appreciate it. Everything is explained above so if you havnt read it the problem is listed above. My mechanic is stumped as well just as many ppl that ive taken it to for some reason alot of the information we have and are getting just doesnt match up. For some reason according to my mechanic and the book he has my computer is suppose to be under the hood next to something to do with the trany, he said where i just cant remember, any way my computer is behind the radio so that is also just kinda werid...any one that could possible shed some light on this problem would be awesome cause im just at a dead end once again....thanks