I have the 04 silverado and using 05 electric fans and 05 GM harness. Need to turn on pin 33 in pcm and pin 42. Pin 42 is turned on but does anybody know if pin 33 can be turned on with 04 pcm?? pin 33 is for the high speed.

 

Anybody please?

 

Read this, it might help. I dont know exactly the answer. Hey but I have a question how are you controlling them with the ECM. In other words how does the computer know when to kick them in to High? When i have gone into HP tuners I have only seen one setting where it only allows when the fans will turn on at a certain Temp. Have never seen anything that would allow the fans to kick into High and Low depending on temperature.

https://ls1tech.com/forums/showthread.php?t=285756

 

I STILL have not hooked my fans up the correct way yet. Maybe this weekend I will figure it out.

 

I have used 05 truck fans, 05 radiator, and the factory harness- plus hooked up pin 42 and pin 33 but all I get is fans on low speed???

 

I think you need to hook on up to 42 and one up to 33. I have made plans to figure this out this weekend, I will post up my findings. The pin 33 is just a theroy at this point in time.

 

I know you guys are going to find out, I just dont understand how the fans know when to kick into high? do you guys know something I dont know? I would also expect since GM came out with these fans on these trucks they would have a setting that would allow them to kick into high when needed and low when not.

 

I did hook up pin 33 and pin 42 and just get low speed.

 

Will know more tomorrow. I have the day planned.

 

I have EFILive and it allows you to choose both fan speeds. Here is the 05 stock programming according to someones 05 BIN that I got somewhere...



You can choose which PCM pins to use (i.e. one speed or 2 speed) and whether to use pin 33 for the recirc door control or for the high speed fan control. I have no idea why GM has the PCM controlling the recirc door for the HVAC in the trucks. Seems like something that should be done by the HVAC control module...

I have the two speed fans with 3 relays hooked up and working correctly under PCM control using the above settings on my 95 truck with the LQ9 and 2002 PCM. I think I will be lowering the temps though, the 05 settings seem pretty dang high.