I need help with programming my fan swap in my 03 Chevy Tahoe.

[sethdipman]

Everything works when you turn it on manually but the PCM just wont turn low speed on at temp, it just goes straight to high speed on the passenger side. All of my electrical connections are good as well as the grounds. Could there be something wrong with the PCM?

[blindsquirrel]

You wouldn't ask questions like that if you studied the fan diagram until you understood it. What would have to happen for only one fan to turn on at full speed?

It sounds like you may have the low/high control wires swapped and going to the wrong relays, or a 'relay 3' (the one that switches the circuit from series to parallel) where its normally closed contacts aren't passing current. Or something like that. It's your truck, you're the only one that can lay hands on it and figure out which wire is going where and if they are all correct and if the relays are the correct parts in the correct locations.

[sethdipman]

You were right, I accidentally swapped the wires to the PCM since one is blue and one is green and the PCM connectors are also blue and green. I matched the colors by accident instead of blue to green and what not. Thank you for your help I really appreciate it!!