Code POI28 - Engine coolant temperature sensor

P0128 - ECT Below Thermostat Regulating Temperature

What is the job you're referring to? Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Lately, my electric fans having been coming on about 30 seconds after starting my truck. They'll cycle on and off throughout the drive.
Engine temp on dash never reads higher than before. Trans temp is steady around 150. Even with the a/c off the fans will run almost immediately after startup.
I've changed the relays and no change.
Next step based on Google troubleshooting is to change coolant temp sensor? Anyone know where it' s located?
Any other ideas what is going on?

what engine? if it's a 4.8 - a 6.2L see pic

It's a 5.3. Thanks for the picture!
I'll give it a shot.

Please let us know how it goes, nice work Hmac300

Changing the sensor had zero impact...
Looks like it is directly related to the A/C system. I can start the truck with the A/C off and the fans will not come on. As soon as I turn the system on, the fans come on within a minute....

it cold be the pcm is for some reason reading an a/c code or a shorted wire activating the fans. there are 5 different diagrams for the cooling fan which includes a couple of things this one doesn't so check the relay marked in pic if that isn't it send your vin back it is either a 3,0,j,or M

does anyone know where the ect sensor is located on a 2008 gmc sierra 1500 with the 4.3 litre v6

Its on left side of engine see location no.8 below

VIN # 3GTEC23J29G223713

ok what I sent is pretty much the same so it's gonna have to be rescanned and then wiring checked from pcm then from pcm to relays to find the problem. or just for the sheer joy of it try unplugging this wire in pic and see if they stay on. it may be the compressor is telling the pcm that I need cooling all the time even when it doesn't work.