GM Performance ECU and Air Conditioning.

Hey everyone,

I am working on a 67 Camaro project. Slowly working my way threw installing a GM Performance LS 525hp crate engine with the matching wiring harness and ECU. The car is also getting a Vintage Air Gen IV upgrade. I am wondering if anyone has been able to make a GM Performance ECU control the air conditioning compressor cut off signal?

This is the signal that turns the A/C compressor off when you go WOT so you don't wreck things. Vintage Air Kit's have an option to hook up a WOT switch that sends a 12V signal to the Vintage Air Control unit when you go wide open throttle. This is left up to . The engine/trans/ecu package I've installed uses a drive by wire system. I am attempting to find a way to avoid making some kind of WOT switch that activates off the throttle peddle since I don't have any throttle linkage to work with. All my research has shown that GM Performance uses their own unique OS, making things tricky.

The wiring harness and ECU instructions/wiring diagrams do not show any kind of A/C output function wires.

I've pulled the ECU file and there are A/C command functions in it which can be changed. This makes me wonder if I can add wires to some of the ECU pins, and what pins the A/C command functions might be on..

The other option I've been wondering. The ECU and Wiring harness comes with 2 Cooling Fan control wires. Both are wired to the same Relay. Maybe it's possible to split this and use 1 wire for the fan relay and 1 to act as an A/C clutch cut off signal??

I've included the file I pulled from the ECU for anyone who wants to have a look at it. Also for fun a link to the video of the first time I fired the motor up. Open headers :)

https://youtu.be/brLJ2bT5iTM

Check these out

https://www.pcmofnc.com/product/gmpp...ric-fan-kit-3/

https://www.pcmofnc.com/product/hot-...-bump-circuit/


The first makes the GMPP harness control 2 fans off, low, high together.
The second will bump the fan speed to the next level when the A/C compressor comes on. So if the fans were off they go to low. If they were low and a/c comes on they go to high. It also has the option to go right to fans HIGH with the A/C on.

Quote:

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Originally Posted by Alvin

Check these out

https://www.pcmofnc.com/product/gmpp...ric-fan-kit-3/

https://www.pcmofnc.com/product/hot-...-bump-circuit/


The first makes the GMPP harness control 2 fans off, low, high together.
The second will bump the fan speed to the next level when the A/C compressor comes on. So if the fans were off they go to low. If they were low and a/c comes on they go to high. It also has the option to go right to fans HIGH with the A/C on.

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Thanks for that info, I'll have to look at that for the Fan control side of things. All though I was asking about A/C Compressor cut off command signal..

My bad.. You might could do a hobb switch on the manifold. When Vacuum = 0 than A/C off. When there is vacuum run A/C that would take care of WOT.

So I've read a couple posts about changing the OS on a GMPP but I seam to have lost track of the posts. Any links people have would be great.

The GMPP hardware is different, if you want to go that direction you need a production E67.

Hi Blindsquirrel, from the research I've been doing the hardware side of it has conflicting information. I haven't been able to figure out what makes the GMPP ECU hardware different then a production E67. The OS is what makes it totally different then a production E67 ECU, from what I've gathered. It's also the OS that guys run into issues with.

I've read info about possibly overwriting the GMPP OS it to gain more of a production type of use. This doesn't seam possible with HPtuners due to how HPtuners performs the write all process. It looks like it's possible using a Tech 2 or MDI 2. I have both, but I've never used factory equipment to change the OS of an ECU. I've only used it to update and replace factory ECU's during normal repair processes.

I am tempted to over wite the GMPP OS and attempt to add in pins to the GMPP harness to see what happens. I am just hesitant since this isn't my car, it's my bosses I am building. Not sure I want to explain to him how I've bricked his ECU if I screw it up.. Most of the info I've read is scattered threw a few posts here and there among various threads I've found. I can't confirm how valid it is. so I've just been looking for more of an open discussion around it.

I didn't say it would brick it, I don't think it will. Others have tried that route to 'fix' the stupid limitations in the stupid GMPP ECMs and found that even with the production OS, the intentionally-disabled features still don't work. If you want it to work like a non-GMPP ECM you need a non-GMPP ECM.

Another mark against it is, how do you get the special GMPP OS back on it if it doesn't work? No VIN = no SPS, and you can't put it back like it was with HPT.

Quote:

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Originally Posted by blindsquirrel

I didn't say it would brick it, I don't think it will. Others have tried that route to 'fix' the stupid limitations in the stupid GMPP ECMs and found that even with the production OS, the intentionally-disabled features still don't work. If you want it to work like a non-GMPP ECM you need a non-GMPP ECM.

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If you've got links to those conversations I'd like to read them. This is some of the stuff I am finding conflicting.

You're right about the GMPP OS and if I remove it, I'd be stuck with out it. Another reason I am asking questions and researching first.

If I was going to look for a used production E67 ECU any suggestion on what years/models to stay way from? what ones to look for?

https://www.google.com/search?tbs=li...uners.com+GMPP
Add relevant keywords to that to narrow it down to specific issues. I don't like them. Mainly, it's that the Editor will make you think that you can change things and get a result, when in reality the ECM ignores the changes. There is a narrow, undefined range of VSS inputs it will read as valid but the Editor shows the same range as the regular E67; the fixed idle speed (may not be on all versions, but certainly is on some); the no-PWM-fan issue... I'm sure there are other annoyances I haven't run across. But those are enough for me.

Find an operating system you like. Harvest the VIN from the sample file, look up which Service Number fits that VIN.

https://www.gmpartsdirect.com/ is a lookup resource I use a lot, but there are many similar that use the same GM database. Has a handy VIN input box on the homepage. VIN, enter, search 'ECM', get Service Number. Manual trans and a swap vehicle, you do not have to worry about OS/ECM compatibility with other modules, you can use any E67 that's compatible with the OS you want to use.

Thank you Blindsquirrel. I've been up and down the google search world which is where I am getting the conflicting information from. We'll see where I go with this project. I have a feeling my boss will want to do a different work around that doesn't involve the ECU.

This is all good information and learning experience for the next swap we are planning after this 67 Camaro is finished.

My God, I haven't seen so much incomprehensible information about the air conditioner yet. You scared me, to be honest, how do you understand all this? Indeed you have worked in the past in some service for the repair of air conditioners. Otherwise, how can you know the wiring? I was also "lucky" recently. For some reason, my air conditioner was leaking very badly, nothing helped me, and I came across an article about it on one site https://www.marvellous.sg/aircon-leaking-water/. And only then I realized that my compression pump had broken, and I needed a replacement. I paid a lot of money to replace this part. Now I will closely monitor my air conditioner and things in general.

Quote:

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Originally Posted by Warentea

I had the same problem with the air conditioner! I couldn't solve this problem for a very long time until I just turned to the service

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Reinstatement of the automotive industry? Osteochondroma due to friction is greater at a woodcut illustration style.