Re: 6.0/4l80 first start
 

So the shop who did the tune said its set at 200. I'm gonna check and see if the ECM is actually disconnecting the ground for the fans tomorrow.

Re: 6.0/4l80 first start
 

Is the 200, on or off temp? Since the PCM supplies ground, and the way you describe it working, you're going to find it's the PCM that's keeping them on, if your wire from the PCM was shorted to ground, it would make the fans stay on, but they would be on all the time, even with the key off. Did you try running it down the road to see if they go off at speed?

Re: 6.0/4l80 first start
 

They are set to turn off at 200. I getting ready to take it down the road now to see if they shut off.

Re: 6.0/4l80 first start
 

And I agree with you ls1 that it's the PCM keeping them on. But the tuner swears it's set at 200.

Re: 6.0/4l80 first start
 

They are not going off at speed. Took it up to 70 still on.

Re: 6.0/4l80 first start
 

Well I'm reasonably sure they are supposed to turn off at highway speeds. Do you have access to any kind of a scanner? Also, not sure if it will work or not, but if you unhook the temp sender it will make the PCM think it's -40*, and that should shut the fans off I would think, of course it will set a code and may force the fans on, not sure because I've never tried it, just thinking out loud. I'm still betting the off temp is set way too low, and isn't actually 200*.

Re: 6.0/4l80 first start
 

ls1nova - Mine failed fans OFF when I overuled the IAT in the process of switching to Speed Density. (solving this with a MAPT)

Re: 6.0/4l80 first start
 

I was referring to the coolant temperature sensor. I wouldn't think the intake air temp sensor would affect it, thats odd.

Re: 6.0/4l80 first start
 

LS1 I have a scanner that's how I've been seeing my temps. It's shows live data and I can also freeze frame with it. When I get home I'll unplug the temp sensor. I'm also pulling my wiring out again and gonna triple check it.

Re: 6.0/4l80 first start
 

Unplugged the temp sensor still stays on. Motor stumbled but other than that nothing else.

Re: 6.0/4l80 first start
 

When we first force-failed the MAF (instead of just removing it) to try SD, it did plenty of strange things. When we tried SD with correction (i forget the proper name for it), I would get bouncing temps. For all I know, the ECM had temporarily pooped itself. Once we had SD dialed in, I never saw another temp or fan related issue, only the false-IAT readings. Go figure.