Any one here running a dual fan set up through the factory PCM on an 07?

I swapped to an E-fan set up yesterday using a set of F-body fans and this write up from trailblazerss.com






After digging around and discovering some of the successful LS1 fans installs on this site, I decided to give it a go. The only shortcoming of the designs that I reviewed was the fact that you need to run an aftermarket fan controller. In order to get around this, I began to research the factory controls, circuits, and pinouts in an effort to use the ECM to control "discrete fans".

The Trailblazer SS uses a fan control routine called "PWM EV", or in other words a pulse width modulated signal for the "electro viscous" fan clutch. The LS2 GTO uses a "discrete fan control" where the ECM provides a ground path for relays that control the fans. Luckily, the C6, TBSS, and the LS2 GTO use the same controller / ECM, it's called the "E40". All of these controllers have the capibility, with proper programming, to pull pin #36 and #56 (blue connector) to ground.

Our TBSS ECM pulls pin #36 to ground already, and that pin leads to a "fan relay" in the fuse block on the passenger side. The output side of the relay sends 12 volts out to the connector that leads to the fan, it's the white wire. Pin 56 is blank on the TBSS, so you'll need to beg your GM service manager for a .064 micro terminal (it's in tray #4 of their terminal service kit, the parts dept. won't have it). If you can't find an .064 micro terminal, then you can use a small gauge wire with about 3/8" of the insulation removed, and push it through the back side of the connector (you need to "knock" out the blank on the back of the connector).

Now that I had the 2 relay control wires ready, I went ahead and copied all the LS2 fan control parameters from a GTO, and imported them in my TBSS tune. This changes the fan type to "Discrete", number of fans to "2", and also takes care of the output state controls and desired fan%. Thanks to the control I have with HP Tuners, this was just a few mouse clicks away.

On to the wiring, I used a total of 3 relays (tyical 5 pole 30/40 amp) that I purchased at NAPA, some relay harness / pigtails, and some misc. gauge wires and terminals. Perhaps I can whip up a schematic, but I'll keep it simple for now. Pin 36 is the "low speed fan control", and remember, this is grounding a relay that's already used in the fuse box (passenger side). The 12v output from that relay (white wire at original fan connector) I'm using to trigger one of the new relays I purchased. Once it triggers that relay, it sends battery voltage to the fan (this relay is full time grounded). Since I wanted pin 56 to operate like pin 36, I had to add a relay where pin 56 could control the ground (just like the OEM relay in the fuse block). Once this relay closes (it's using the same white 12v trigger wire as the other add on relay with pin 56 as the ground switch), it sends 12v to the other add on relay. This last add on relay can then close and send a full 12v to the "high speed fan". It should be noted that all of the grounds for the relays are brought to the same point, the bolt that secure thes horns down below the battery. I need to add a fuse on the main 12v power leads to the relays, I'm just not sure what size / rating of fuse??

This sounds complicated, but it was really easy, and a schematic would be a bit easier to decipher. The fans do work as expected, and I've got mine programmed for low speed on at 196, and high speed on at 203.







2 problems I have run in to.


1) Pin 56 on my blue ECM connector has a wire in it.
2) When wiring it up using the white wire from the original fan clutch connector, it pulses the fans on and off every 5 seconds until it reaches temp then they stay on and never turn off.


Here is how I was originally going to wire it:







Here is how it is wired right now:






Does the 06 use a different ECM/TCM than the 07?
Anyone get a 07 working through the PCM?

I'm tempted to wire up the fan controller I bought from Summit and not worry about it, but I would really like to have control of a low/high speed fan through the factory ECM.

Any advise would be great.

Shaun

 

"Anyone get a 07 working through the PCM?"


ADM Performance has had 2007 for a while now.I believe his controller can easily run 2 fans at variable speed from what I have read,almost a year ago.

 

Let me add to that, with out having to send your pcm to someone else.

I have the system working. There isn't a low/high, but both fans come on at 196 and off at 192. Stick about 189 on the freeway and I have not seen it go over 198. AC on also fires up the fans at any temp.

It is wired like my second diagram.

Definate differance in mileage.

 

I'm a noob here, but what is the advantage of this over the stock fan?

 

e-fans rob less horsepower from the engine and not noisy like the mechanical fan.

 

Thanks. I may have to look into that for my SSS then.

 

I pull a 22' bay boat on the weekends. Is there enough cooling capacity with the electric fans? or should I stay with the factory fan?

 

I pulled my heavy utility trailor today along with a 63 longbed (frame and bed no cab). Total weight was 9600lbs (including the TBSS) and I did not see any ill effects. If I was towing for a long distance I would definately get a big trans cooler though.

 

Did you ever get this figured out.....my buddy just bought some LS2 GTO fans for his TB SS and we are trying to figure all the electrical out before we start on it.