I have checked all the pins on my PLCC socket on my PCM board with a multi-meter set on BEEP mode. But I absolutely cannot figure out where these to pins trace to. Does anyone have a PCM schematic or know where these two pins trace to?

This is on the BLUE/GRAY T-Side of the board.

FULL SIZE PICS
http://i178.photobucket.com/albums/w...s/ecm_pins.jpg
http://i178.photobucket.com/albums/w.../ecm_pins2.jpg

 

The datasheet for your an28f512 shows both as N/C

 

Wow what the heck your right! I'm looking at the datasheet myself and sure enough it shows PINS 2 & 30 = NC

They must serve some sorta purpose though because on another PCM board that came from a 94 camaro I was able to find the location of pin 2 which is that 3rd pin down in the picture above. But what's weird is that the board is a little different than the 95 board. I'm thinking that there must have been some kinda revision made later on in the years. In any case I still cannot find where the two pins trace two on my board.

That is weird though cause on the datasheet it says "NO INTERNAL CONNECTION to device. Pin may be driven or left floating".

 

I'm curious about the differences you found in the 94 vs 95 boards.

Are they both F-body PCMs?

Post some pics showing the differences?


As for pin 2 - where does it go to on the one board?

 

Alright here are the two boards side by side. I wouldn't say that the difference is because one is 94 and the other is 95 because I have had 94 ECM's that looks IDENTICAL to the 95 so I don't think that's the difference. But whatever the difference is you will notice that the ECM on TOP has LESS CHIPS than the BOTTOM one. But the top one is the exact same board that I have seen time and time again. The bottom board is the first I have ever seen of it's kind. All the other 94-95 ECMS that I have ever seen look EXACTLY like the board on TOP.
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Now take a look at this picture. This is where I was telling you how even though it says on the datasheet that there is NC to this pin but yet I was able to trace it to another spot on the board. You can note this from the first picture as well. This is on the BOTTOM ECM in the picture and like I said before this is the first one that I have seen like this. I was not able to trace the two pins in the TOP ECM.
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Well I finally figured out what the problem was and it had nothing to do with the two pins that I couldn't trace either. Apparently those pins really serve no purpose after all. But my problem was that when the flash chip was removed from the socket I was getting contact to all of the pins. I checked each and every one of them and they were all fine. But then on a hunch I put the flash chip in the socket and I found a pin that wasn't making contact with the chip installed. So it turns out that it needed to be soldered down a little bit more. I guess that when the chip was removed the pin was sitting freely on the contact pad, but with the chip installed it was causing the leg to lift off the pin thus not making any contact. So I soldered it back down and all is good now. Man what a PITA lol

 

"more chips" = "Y-body PCM"

 

Ohhhh is that what the deal is. So then what's diff about the Y-Body PCM? Why the need for the extra chips?

 

The Y implements partial OBD2. The main thing is there's a third O2, which means you need hardware to read the 3rd sensor.

Doesn't make sense to me that you need 4 chips to do just that, so I'm sure there's other functionality in there, but I've never seen it discussed online.

Maybe all of the code for the OBD2 monitoring is in the separate chips. Are there any useful markings on those chips?

Thanks for the pics - I'd never seen the two side by side until now.

 

Something else interesting that I found today.... A flash chip that has a different PN and when I try to load a file on it with Tunercat I am getting an "Incorrect Vendor/Version Code" error.

Notice how the top chip is a Q1351 and the bottom is an AN28F512. Well apparently the two are not interchangeable.

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