Thread: Electric Cooling fans behaving strangely

So I've been getting the P0128 for about three years now. I've replaced the thermostat (195) several times, the ECT sensor a few times, the wires to the ECT, tested and replaced the IAT sensor too. The code comes and goes. I've been noticing lately my engine temp running upwards of 240 when I'm sitting still, also. I can rev the engine and usually knock it back down. I had the engine code in, and was checking the resistance again on my ECT sensor and IAT, when I noticed that after I started the engine cold, when it was 30 degrees outside and neither the heater or air conditioner on, both of my electric cooling fans turned on. They didn't turn off until about 180 degrees. I turned the car off, and came out later when the engine was still relatively warm, let the car run, and it ran almost all the way up to 230 without the electric fans ever coming back on. This seems pretty back _sswards to me. I'm not sure where the fans get their input from besides the PCM, and it occurs to me this odd fan operation may be causing my intermittant p0128. Does anyone have any input? I've got a 2001 GTP btw. No mods except K&N air intake.

My mirror has the outside temp on it, my DIC doesn't. The temp on my mirror is usually accurate within five degrees I'd say. The outside temp sensor affects the radiator cooling fans?

Good to know. So I went to check my relays by swapping the cool fan 1 and 2 relays, but of course they were working properly. Low coming on around 223, cutting off somewhere around 195-205, not sure. But they were working how they were supposed to. I swapped them anyway just to see, no difference. I will wait to try a cold start again and see if I can duplicate the problem, then swap them and see if it makes a difference. If the cool fan 1 and cool fan 2 don't make a difference, I might try and get a new cool fan relay (the black one) and see if that helps. Thanks!