2006 Yukon Denali E fans not working

[Slow yukon]

Have a 2006 gmc Yukon Denali with. E fans. So I had the engine rebuilt. But when I got it back only the passenger side E fan works and only in high. Fans were working fine before the rebuild. I checked all relays and fuses already. If I take the passenger side connector and put it on the driver side fan the problem follows so I know the fan works?
Any help is appreciated

 

[TJ Baker]

Have a 2006 gmc Yukon Denali with. E fans. So I had the engine rebuilt. But when I got it back only the passenger side E fan works and only in high. Fans were working fine before the rebuild. I checked all relays and fuses already. If I take the passenger side connector and put it on the driver side fan the problem follows so I know the fan works?
Any help is appreciated

Have you tried swapping BOTH fan connectors?

 

[Slow yukon]

Have you tried swapping BOTH fan connectors?

View attachment 490271

Yes I tried that and the problem follows

 

[ScottyBoy]

Coolant temp sensor is possibly bad, or simply unplugged. I remember reading about this same exact issue once before and several folks commented that the ECM has a failsafe to run a fan on high when the coolant temp sensor is defective or giving erratic readings.