Overheating 08 Tahoe when driving slow

[Doubeleive]

Hey guys I have a 2008 Chevy Tahoe with the 5.3 LS and 252k miles with a rebuilt engine.

Recently it has developed an overheating problem but only when going slow(35 and under) then when I speed up it instantly goes back down. I don’t really have any more information on this issue. I do have an engine light on but last time I checked that it was for something different. Im going to check the codes again later to see if there is anything.
Has anyone had this problem before and what could it be?

check the electric fan harness & the motor plug side also, at one point there was a recall because the harness would melt. the fix was to replace the harness end with slightly thicker wiring. this is a example of what to look for but sometimes the wires melt behind the harness plug

 

[petethepug]

So much awesomeness. Picture says 1000 words. Cajun style harness connectors.

 

[petethepug]

Well, what are the results of the crack the beer test?

 

[danrduc]

Fans may not be going on high speed mode, relay not grounding for high speed. I had that happen recently in the summer.