cmaurice876

Hey everybody, I am about to dive in to building my standalone 04 GTO harness to go in a 77 corvette. I began reading and realized that the low speed fan is controlled by the BCM for some reason during this year model for the GTOs. I would rather not have my pcm flashed again to program a new pin to control the low speed fan and I do not have a BCM from the GTO. Is there any way around this?

Thanks a lot

arthropraxis

You could use a relay system controlled by a temperature sensor to control the low speed fan. I would just get it flashed again. Most people can do it overnight and it only costs about $75 maybe less if you only need that done.

aknovaman

iTrader: (7)

Chk your email for the requested schematics.

cmaurice876

thanks a lot man for the schematics man. I am just a little confused on how the pcm and bcm communicate in these GTOs. I do not have the bcm, but I have the PIM and some type of throttle position box. Do I even need the PIM and the throttle position box?

arthropraxis

I am using a 2004 GTO for my build and am not using anything but the ECM. The BCM and PIM are used for gagues, A/C, the fan of course, traction control and some other functions unused in a stand alone system.

Here is some good info on the fan wiring http://westersgarage.eidnet.org/Fan%20Harness.pdf .

If you are using A/C the BCM controls A/C request to the ECM.

cmaurice876

hmm we are definitely planning on having air condition. So how would the a/c work without the bcm? Is there something that would need to be flashed within the pcm?

battery1882

iTrader: (1)

thanks for sharing that!

arthropraxis

The A/C request coming from the BCM is the Achilles heel of this particular motor. I haven't seen where anyone was able to flash it to control the A/C request. I was able to get an A/C request signal from the cars HVAC system wired directly to the compressor. With mine when the A/C is triggered it turns on high speed fans. You should be able to wire that up with relays. All you will lose is idle up with the compressor.

aknovaman

iTrader: (7)

Have your tuner load a 2004 truck operating system in the 2004 GTO PCM, mod the fan settings for e-fans, import the GTO engine parameters as well as the trans settings. Stick a fork in it and be done.

kendogg

iTrader: (2)

This. Also, for what pins to add for high & low speed fan settings:

http://www.lt1swap.com/2004vortec_pcm.htm

arthropraxis

When you say load the 2004 truck operating system do you mean the A/C table or the whole system? Does the truck system have the same blue and green connectors? I know of someone else that is too deep in his swap before he found out the A/C won't work with the ECM.

cmaurice876

I see that the green connector does not have the A/C request pin, but it has A/C refrigerant pressure sensor signal ( which I assume is equivalent to the low pressure switch signal), the A/C clutch relay control, and a A/C compressor clutch supply voltage -- for cooling fan and Idle control signal. Wouldn't this last one be able to control the idle up and the for the high speed to kick in? Do you have any more information on how you got your A/C request signal?

Thanks a lot guys

arthropraxis

I am not sure what gets put into the equation for idle up when the compressor comes on. I was more concerned with the fan controls. The high speed fans should come on with the A/C request.
On my particular swap I connected the car's A/C request line to the GM connector. The ECM never sees to A/C turn on. It hasn't been started yet but I have been assured the motor can take the torque of the compressor coming on.

aknovaman

iTrader: (7)

The PCM file needs to be set up cprrectly, not operated via the data bus (BCM). Did it on Miata with a 2004 GTO drivetrain.

Go here and scroll down to the bottom for the answer;

http://forum.miata.net/vb/showthread.php?t=415921

cmaurice876

Alright one more question. So we started tearing into our wiring harness. One thing that we don't understand is the neutral safety switch. Why is there know CPP or neutral safety switch signal in the pinouts for the pcm? We have found that the same plug that gives power to the injectors and the coils also has a grey/blue wire that supposedly controls the neutral safety switch. Any ideas?

kendogg

iTrader: (2)

As far as I know, the PCM doens't need a neutral safety switch signal for anything.

aknovaman

iTrader: (7)

Load a savanah van file that has manual AC , not operated via the GM databus but via the AC request wire.
PN is used to change the idle speed among other little stuff. Folks that car dies when coasting or coming to an abrupt stop do not have the PN and in-gear tables set up correctly. Making them the same values works fine. BTW, manual trans does not need a PN switch and I have never used one on the harness I build.

arthropraxis

Thanks, I will pass that info along.

2xLS3

iTrader: (3)

IIRC it needs to do a crank relearn to clear the P1336 code

Hybrid Builder

Anyone know where I can get the Savanah van file? I have HPTuners, and cannot find a file to do this. I would like to give it a shot, I have the 2004 GTO engine as well, and am trying to get the A/C request working. Thanks!