Locked 2 PCMs

C5Shark · Post by **C5Shark** » Mon Dec 11, 2006 4:44 pm

I tried my hand at tuning and locked 2 of my PCMs. I have a 95 LT1 Caprice. I started with a tune from Bryan Herter and that program ran fine. I wanted to drop the idle a tad, and modify the performance shift tables. I did so and went to load the program. It finished loading & said it was successful (Winflash), but when I went out to the car I had a flashing CEL, fans were on, and the PCM would not communicate. Same thing happened to another PCM. The guys at the ImpalaSS Forum told me it was likely an incorrect checksum. I checked that with the checksum utility from TC and the ISSF guys were right, the checksum was incorrect. That program let me correct the checksum, but now I'm out of good PCMs lol.

What I want to verify is that, when I modify a file in TunerPro R/T & check the checksum with the utility, the file is them ready to load. Or is there something else I'm missing. I can't afford to keep locking PCMs all willy nilly like this. lol

Post by **Mangus** » Tue Dec 12, 2006 8:23 am

It depends on the XDF you're using. Older EE.xdf files didn't have the checksum set up correctly. The one that is currently up on Moates appears to have the proper checksum set up.

To verifiy if the definition you're using has the checksum properly set up, open the definition in TunerPro and hit Ctrl + F2, click the checksum tab, and ensure that a checksum calculation is present. Click "edit selected" and verify that data start is 2018, end is 10000, and store is 2015 (Store size is 16-bit, data size is 8 bit).

You should be able to have your PCMs recovered. I believe that Moates has the ability to do this as well (or will soon if he doesn't currently).

I highly recommend removing the checksum altogether by setting the mask ID byte ($EE) to $AA.

C5Shark · Post by **C5Shark** » Tue Dec 12, 2006 11:33 am

Recovered how? I'm having a buddy pull the bad flash chips, and put in some new ones. He's also socketing it for me just incase I screw up again, apparently the old chips can be reflashed in an EPROM programmer (I think thats what I was told) and used again.

Are there any negative effects that removing the checksum will have? What is the purpose of them checksum?

Post by **Mangus** » Tue Dec 12, 2006 12:48 pm

Yes, that's how you recover them - reflash the chips.

No, there are generally no negative effects when disabling the checksum, and it would avoid the issue you ran into (although do would using the newer version of EE.xdf).

C5Shark · Post by **C5Shark** » Tue Dec 12, 2006 1:05 pm

It's probably an older version if EE.xdf. I don't remember where I downloaded it from.

Post by **Mangus** » Tue Dec 12, 2006 2:56 pm

Get the one here:

http://www.moates.net/fileman/index.php?dir=3)%20Binary%20Editor%20Definitions/1)%20TunerPro%20XDF%20Files/1%29%20General%20Motors

C5Shark · Post by **C5Shark** » Wed Dec 13, 2006 1:53 pm

Thanks. So with this file, when I save my changes it is ready to load, nothing else needs to be done to it before I flash the PCM. Sorry for being repetative, but PCMs are expensive lol.

I want EE.xdf correct? I've seen some mention of EEB on the ImpalaSS Forum but don't know the difference (if any)

Post by **Mangus** » Wed Dec 13, 2006 2:05 pm

I'm not too sure about the difference between EE and EEB either. You'll have to investigate that.

Yes, the EE.xdf that is there should work fine. Before flashing the PCM, make your changes, save the bin, then verify the checksum with your checksum application just to be sure. If it works the first time, you're good to go. You may also choose to disable the checksum routine by uploading AA to the mask ID byte.

-M

C5Shark · Post by **C5Shark** » Wed Dec 13, 2006 2:20 pm

Ok, thanks. It'll probably be atleast another week before I get my hands on a working PCM so now I play the waiting game. lol

C5Shark · Post by **C5Shark** » Thu Dec 14, 2006 12:32 pm

I looked at the settings by hitting Ctrl + F2 and the checksum values were exactly as you posted. I downloaded the file from the link and I'm still getting incorrect checksums. How do I disable the checksums completely? I don't know where to find the mask ID field.

Post by **Mangus** » Thu Dec 14, 2006 12:39 pm

I'll investigate further when I get home.