Electric fan upgrade in '03 Tahoe

Hi,

I just installed a OEM electric fan instead mechanic fan in my '03 tahoe, I bought electric harness from Nelson Perfomance. The cuestion is, How can I activate the pulse (pin 42) into the PCM?? cause when my 'hoe is hot the fans doesn't start on, only one fan starts when A/C compressor is running. I appreciate your help

You will have to go to a dealership or a mechanic that has a Tech 2 Programmer and have them reprogram the PCM. Only thing is, I am not 100% positive that the PCM can be programmed for an output on pin 42 of C1 in the 00-04 models. This pin is used for low speed cooling fan relay on the 05-06 models with the stock electric cooling fans. Prior to 05 year models, C1 pin 42 has no function. I believe this pin can be programmed to output a signal referenced from the CTS sensor if I'm not mistaken. Hopefully the Tech 2 tool will be able to reprogram and produce a signal for that pin for your set-up.

Oh yea. And make sure it is pin 42 in the C1 BLUE connector. C1 is blue. C2 is red.

Of course I'm sure to pin 42 is from C1 (next to engine) and it was empty, so I need some more information about CTS sensor reference because I found a guy with have Tech 2 but he told me that he can't activate this pin (He never perform thi kind of modification, thank you in advance

I call to Nelson Performance and they told me that is possible to set PCM's pin42 through Predator or Hypertech programmer so, somebody can support that in their experience?? it is order to make the desicion of buy/or no a programmer, thanks

rcaballe said:

I call to Nelson Performance and they told me that is possible to set PCM's pin42 through Predator or Hypertech programmer so, somebody can support that in their experience?? it is order to make the desicion of buy/or no a programmer, thanks

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I'm not sure. I believe you can adjust the turn-on temp on 05-up trucks. But I don't know if you can make any adjustments on a signal that isn't present, unless the signal can be programmed on/off. Though I am not 100% sure, my best guess would be that it can be programmed. And if Nelson Performance agrees and is able to provide some sort of gaurantee relevant to their statement, then I would try it.
I wish I had more solid info for you.