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Thank you for such quick response. I realize that the IAC drivers are unrelated to the AC request function. However, according to LT1SWAP.com, only PCM's with IAC hardware will allow for the Analog AC request function (as opposed to the serial). My old truck don't know from serial, so I'd like to switch to the analog, 12V AC request mode. What I'm asking is since most OS's in the 2004 years expected to use serial, don't I need to configure the OS to use Analog? And if so, can that be done in TunerPro?

Quick follow up. The relevant section of lt1swap.com/airconditioning.htm is:

"A/C Request: This is a signal input to the PCM indicating the drivers request for a/c activation. There are two ways this is done from GM, a physical wire, a 12v+ positive signal on Pin 17 on C2 PCM connector, and a serial data request over databus. RED/BLUE pcms used 1999-02 all support 12v+ positive signal a/c request. BLUE/GREEN 2003-07 the only pcms that will work with physical a/c request are: Service Numbers: 12576106, 12581565, 12586243, 12589462, 12602801. If your PCM Service number is different from these listed, a/c request input WILL NOT WORK."

Interesting, I was not aware of that. I don't believe the difference is related to the IAC drivers, but that doesn't mean that those service numbers don't have additional hardware differences in addition to the IAC drivers. The relevant parameter would be "A/C System type". I don't know if any of the 12587603 XDFs have that parameter defined. I have an XDF for 12212156 (P01) that has that parameter, but that doesn't help you. I believe HP Tuners has that parameter for 12587603. If you have access to one of their dongles, you can read the PCM without licensing it to verify how it is configured if you just want to check it. What vehicle was it removed from? Be very cautious using the 12587603 XDF for 12606960. I know for certain that the 12587603 XDF doesn't align fully with 12606960. I wouldn't recommend using it.

I'm not sure that there is a 100% correlation between IAC and analog AC request hardware installation in the Blue/Green PCM's. My reading of various forums says that there is at least a significant overlap. Meaning IAC equipped is a good predictor of analog AC equipped. In any case, I think I have a PCM that should work from the hardware perspective, now it's just a matter of the programming aspect.

The vehicle that provided the engine was a 2004 Sierra 4x4 with ls 5.3 LM7. The vehicle that provided the PCM with the IAC driver is a 2003 Avalanche 4x4 also with the ls 5.3 LM7.

And thanks for your suggestion of just swapping in the complete 12587603 OS. I'd already figured that was going to have to happen. But no, I don't have any HP Tuners hardware or software. Was hoping to avoid all that. Really prefer the DIY approach using community-based tools!

By the way, my follow up question was going to be, once I swap in the 12587603 OS, would I need to segment-swap in the engine calibration from the original donor PCM, or is the new OS likely to run the LM7 just fine? I will also use the 4l60E. Would I need to segment swap something in for the transmission as well? Complete newbie here, so...

How to disable post cat o2 sensors in the right manner? Just disable DTC or there would be impact on fuel trims or smth like this. Cat deleted, so the sensors 2 can be removed.

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Originally Posted by rocketmench

I'm not sure that there is a 100% correlation between IAC and analog AC request hardware installation in the Blue/Green PCM's. My reading of various forums says that there is at least a significant overlap. Meaning IAC equipped is a good predictor of analog AC equipped. In any case, I think I have a PCM that should work from the hardware perspective, now it's just a matter of the programming aspect.

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Sometime in the (probably distant) future, I'd like to examine the hardware, and verify that there is in fact a difference. It seems unlikely to me that GM would omit hardware for an input, unless they wanted to repurpose that pin as an output. It is possible that the input is there, and the difference is in software, and the information is out of date. I'm not saying that is the case, but until I see it for myself, I'm not ruling anything out. If there is a hardware difference, it could be as simple as a few omitted components that could be added to regain that functionality, as is the case with the IAC driver.

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The vehicle that provided the engine was a 2004 Sierra 4x4 with ls 5.3 LM7. The vehicle that provided the PCM with the IAC driver is a 2003 Avalanche 4x4 also with the ls 5.3 LM7.

And thanks for your suggestion of just swapping in the complete 12587603 OS. I'd already figured that was going to have to happen. But no, I don't have any HP Tuners hardware or software. Was hoping to avoid all that. Really prefer the DIY approach using community-based tools!

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I totally agree. I do have HP Tuners. If you want to upload the bins you have, I can flash them into a spare PCM and read them out and upload them in HPT format. That way you can look through them and compare.

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By the way, my follow up question was going to be, once I swap in the 12587603 OS, would I need to segment-swap in the engine calibration from the original donor PCM, or is the new OS likely to run the LM7 just fine? I will also use the 4l60E. Would I need to segment swap something in for the transmission as well? Complete newbie here, so...

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Either should run the LM7 just fine. If the Avalanche had a 4L60E, you should be able to run that calibration. If not, you should be able to segment swap the transmission segments. The post you referenced indicated that most segments, including the trans segments align.

Thanks so much with your offer to read the bins. Hopefully my attachments work here. Note: the bin labeled "2GTEK.bin" is the one from the donor truck. When I read it, I found the vin didn't match the truck so maybe the PCM was replaced at some time. It's very similar though, a 2004 Silverado LM7. This is the one supposedly without analog AC request, Service number 12586242 with OS ID 12606960.

The bin labeled "3GNEK.bin" is the one from the IAC enabled pcm with Service number 12576106 and OS ID 12579405.

I did try to trace the pins on the IAC enabled pcm but couldn't find any connection from C2 Pin 17 to anything else on the board. I'll see if there's a difference to the other PCM in that location and let you know.

So I opened up both PCM's and looked for differences near C2 pin 17, which is the input for the 12V analog AC request. As you can see in the attached pdf, there are 2 resistors in the Service No. 12576106 (with the IAC) that are missing in the 12586242 PCM (without the IAC). There is a 100 kohm resistor on the backside, and a 3 kohm resistor on the front side that is missing.

There are some other minor differences, so I don't know if it's simply a matter of populating those missing resistors to restore the ac request functionality. In the 12576106 PCM, on the backside, immediately to the right of the 100 kohm resistor there appears to be a capacitor to gnd. In the other PCM, immediately to the right of the missing 100 kohm resistor there is instead another resistor.

I still could not find where pin 17 leads to ultimately. Presumably, at some point it finds its way to the main CPU.

The IAC board uses an Intel flash, whereas the non-IAC board uses an AMD flash.

Nice work. I don't have the time to convert the bins for you today. I'll try to get them for you tomorrow

Updated my document a bit to clarify a little. I also added the actual circuit for analog AC request as I now know it. I was able to find the "destination" of the C2 pin 17. It goes a chip labelled "203 466", pin (I think) 8. Without a data sheet, which I could not find, I have no idea what the function of that chip is but it has the same foot print of the 11124 466 chip which is apparently a "datalink controller" at this PCM hacking link: https://www.thirdgen.org/forums/diy-...-101-step.html.

To sum up, if one were daring, one could populate the missing 3k and 100k resistors, find out the value of the missing capacitor, and replace the 10k resistor with the cap to restore ac request functionality to the pcm's without that capability.

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Originally Posted by rocketmench

Updated my document a bit to clarify a little. I also added the actual circuit for analog AC request as I now know it. I was able to find the "destination" of the C2 pin 17. It goes a chip labelled "203 466", pin (I think) 8. Without a data sheet, which I could not find, I have no idea what the function of that chip is but it has the same foot print of the 11124 466 chip which is apparently a "datalink controller" at this PCM hacking link: https://www.thirdgen.org/forums/diy-...-101-step.html.

To sum up, if one were daring, one could populate the missing 3k and 100k resistors, find out the value of the missing capacitor, and replace the 10k resistor with the cap to restore ac request functionality to the pcm's without that capability.

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My guess is the resistor that is in place of the the capacitor is there just to keep the unused input low. The 3k is a pull down and the 100k resistor and capacitor are probably for debounce. I think there's a very high probability that adding those components will enable the functionality. I'm still surprised that they weren't all populated the same. It's probably less than $.02 worth of components. I'd try it but I don't have a vehicle to test on. My van is 0411 swapped, but I haven't done a 24x crank trigger yet and I haven't installed A/C yet. The plan is to install the 24x reluctor, LS coils, P59 and DBW. So many things on the to do list.

It looks like I'm not going to be able to get those bins converted to HPT today. I can't find my HPT dongle. I think it may have fallen out the door of my step van :(

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Originally Posted by Neukam

It looks like I'm not going to be able to get those bins converted to HPT today. I can't find my HPT dongle. I think it may have fallen out the door of my step van :(

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Nope, I found it. Yay!

I think you may have sent me the wrong file. The 2GCEK file is from a 2003 Silverado with a 4.8L and both files have OS 12579405

Yes, you are right. I messed up. I have 4 PCM's and bin's and I mis-read the name. Here's the one from the 2004 Sierra that provided the engine I want to put in my 68. Now, what I found from TunerPro is that it's not a 2004 Sierra VIN, it's a 2004 Silverado VIN in the OS. Not sure if the PCM got replaced at some point or if the guy who undid the vats changed something on me.