pcmhacking.net

Hi all, not sure if I stumbled onto something here or not but I'm going to investigate further. I have a 2004 GMC Envoy XL with a 4.2l (P10). I have been attempting to try and tune it for some time now. I was able to find a matching bin and xdf file, and edit it using Tuner Pro. When I attempted to write it to a spare pcm, on a bench harness, with PCM hammer, it said the segments that I edited were bad. Before I made any changes to my spare pcm, I installed it in my Envoy and it ran fine. For shits and giggles, I opened up the bin in Universal Patcher. I was able to see the changes that I made in Tuner Pro, and I made a couple more using Universal Patcher, and save the file again. I tried again to write it to my spare PCM, using PCM hammer and it worked. All segments were good, and it successfully wrote with no errors. When I get a chance, I'm going to put this PCM in my vehicle and see how it runs.

Any input, or anything I'm missing would be greatly appreciated!

Vetteyog wrote:Hi all, not sure if I stumbled onto something here or not but I'm going to investigate further. I have a 2004 GMC Envoy XL with a 4.2l (P10). I have been attempting to try and tune it for some time now. I was able to find a matching bin and xdf file, and edit it using Tuner Pro. When I attempted to write it to a spare pcm, on a bench harness, with PCM hammer, it said the segments that I edited were bad. Before I made any changes to my spare pcm, I installed it in my Envoy and it ran fine. For shits and giggles, I opened up the bin in Universal Patcher. I was able to see the changes that I made in Tuner Pro, and I made a couple more using Universal Patcher, and save the file again. I tried again to write it to my spare PCM, using PCM hammer and it worked. All segments were good, and it successfully wrote with no errors. When I get a chance, I'm going to put this PCM in my vehicle and see how it runs.

Any input, or anything I'm missing would be greatly appreciated!

Universal Patcher automatically fixes any checksums when you save the file.
Tunerpro can be tricky and probably needs a plugin for the P10 ecu's to correct the checksums..
Other than that it sounds like you got done what you needed to..

ironduke wrote:
Universal Patcher automatically fixes any checksums when you save the file.
Tunerpro can be tricky and probably needs a plugin for the P10 ecu's to correct the checksums..
Other than that it sounds like you got done what you needed to..

Yes, what I am really interested in is transmission tuning so I will see if it works and report back.

Okay, got my Envoy to run with the new PCM and modified tune, but I am getting a P1680 code and I have no throttle. My thought is because it's a different PCM it is not communicating correctly with the bcm. Is there a way to sync them together? I also deleted all the VATS settings in the tune.

Any suggestions will be appreciated, thanks!

I do not know the relearn process, however some clarity for the knowledge banks would be helpful ...

1. The original OsID on your Envoy is ??
2. The Original OsID on your Spare is ??
3. They both ran your Envoy correctly (including Throttle using spare PCM) ??
4. You did an Os change to the Os of the only XDF available 12587430 ??
5. When you did the Os change you did a 'Write Full Flash (clone)' ??

It's possible that had you done a 'Write OS, Calibration & Boot' it may have worked, the throttle calibration info is stored in the Parameters Section.
Possibly writing the Parameter section of the original Envoy PCM to your spare will solve your throttle issue, it won't hurt to try and it will be educational.
However, if it doesn't work, you should write the parameters back from the New OS (12587430). The parameter section should match the OS in case they are different (even though the Os will overwrite whatever is there).

Remember, the OS uses the Parameter section to save parameters it needs to store between runs (if they change), like throttle sync data, learned fuel trims, etc..., etc...

-Enjoy

I think this because you changed OS, and PCMHammer does not write the 512 bytes or so of slave CPU data. I think thats where the electronic throttle stuff is. You'll need to go back to the original OS and edit it with universal patcher. If you want to change OS, then probably the only way at the moment would be to do a reflash with techline as I think that'll write the slave. Similar problems to on E38s with the slave and OS changes and tools that dont write it.

If we were to write those 512 bytes we'd have a whole lot of learning about how to access it on the P10, as currently we dont know how and the GM SPS process is a bit magic. Its inside the CPU, not in the flash chip, so its different to the main flash.

Whoops, forgot about that and I agree it's likely what handles the throttle.

-Enjoy

Gampy wrote:I do not know the relearn process, however some clarity for the knowledge banks would be helpful ...

1. The original OsID on your Envoy is ??
2. The Original OsID on your Spare is ??
3. They both ran your Envoy correctly (including Throttle using spare PCM) ??
4. You did an Os change to the Os of the only XDF available 12587430 ??
5. When you did the Os change you did a 'Write Full Flash (clone)' ??

It's possible that had you done a 'Write OS, Calibration & Boot' it may have worked, the throttle calibration info is stored in the Parameters Section.
Possibly writing the Parameter section of the original Envoy PCM to your spare will solve your throttle issue, it won't hurt to try and it will be educational.
However, if it doesn't work, you should write the parameters back from the New OS (12587430). The parameter section should match the OS in case they are different (even though the Os will overwrite whatever is there).

Remember, the OS uses the Parameter section to save parameters it needs to store between runs (if they change), like throttle sync data, learned fuel trims, etc..., etc...

-Enjoy

Thanks for the reply...
#1 original OS is 1258-8430, no xdf available for that and I'm aware of.

#2 I am unsure of the original OS on the spare pcm, but it is out of a 2004 as well.

#3 my Envoy obviously ran fine with the original PCM in it. I did flash the file from my 2004 into it and it ran.

#4 yes, I did an OS, calibration & boot write with that OS , but not a clone. I also changed the VIN to my vehicles and disabled all the VATS that I could.

Is the label still legible on the spare PCM? I might be able to tell you which OS it had if you can post the numbers from the label.

The contents of both new and old labels would be ideal.

I question the 125 88 430 OsID ... That is not an OsID that PCMHammer currently recognizes.

As Gatecrasher asked, it would be great if you could post images of both PCM's labels if they have them ...

It would be beneficial to the community to get this info correct!

-Enjoy