PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Assistance starting out tuning.

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Old Aug 6, 2025 | 10:10 AM
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Default Assistance starting out tuning.

I'm going to find out if my current tune is locked or not, provided it's unlocked I'm planning on buying HP Tuners so I can make minor modifications myself. I've got a couple of changes I want to do to my shift points initially. Is this something I can get help with here as a complete newbie to tuning?
I'm very happy with the tune but I'm sure with a bit of time I'm hoping I can get a couple of minor things improved to it to just how I like them.
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Old Aug 6, 2025 | 10:36 AM
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Learning to datalog the correct information and understand it is probably the hardest part.
Once you get that down, adjusting the tune is not that bad.
Youtube of course is your friend here.
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Old Aug 6, 2025 | 01:43 PM
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What year and model?

If it's 99ish-07ish you might be able to do what you want with an OBDX Pro interface ($100ish) and PCM Hammer or LS Droid (both are free) and Tuner Pro (also free).
The free/cheap tools are not as friendly as HP Tuners, but they cost almost nothing and they're (slowly) getting better.
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Old Aug 6, 2025 | 04:34 PM
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Question for NSFW: What major difference(s) between interface devices: OBDX Pro VX vs GT ?
Assume they are both capable of re-writing PCM tune, is one superior/faster than other?
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Old Aug 6, 2025 | 06:23 PM
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If I remember right, the VX only works with the VPW-based PCMs (P01, P59, 99ish through 07ish), whereas the GT supports CAN and some other non-GM protocols.

For the PCMs that PCM Hammer supports, they're basically identical. I have one of each, I do a lot of testing with PCM Hammer (because I've worked it a lot) and I haven't noticed any differences.
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Old Aug 6, 2025 | 08:02 PM
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Originally Posted by NSFW
What year and model?

If it's 99ish-07ish you might be able to do what you want with an OBDX Pro interface ($100ish) and PCM Hammer or LS Droid (both are free) and Tuner Pro (also free).
The free/cheap tools are not as friendly as HP Tuners, but they cost almost nothing and they're (slowly) getting better.
I'm in Australia. My car is a 2002 Holden Monaro, the early equivalent of your 2004 GTO.
I did look into the free tools but I don't really want to do a tune from scratch, just be able to make some minor changes to my current tune.
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Old Aug 7, 2025 | 01:26 AM
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If your car was tuned with HPT, and if the tuner locked it, then HPT won't allow you to edit that tune - you'll have to start from scratch.

But I don't know which PCM is in your vehicle, so I don't know whether PCM Hammer or LS Droid will work at all. But they will work fine with most "locked" tunes.
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Old Aug 7, 2025 | 07:07 AM
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Originally Posted by NSFW
If your car was tuned with HPT, and if the tuner locked it, then HPT won't allow you to edit that tune - you'll have to start from scratch.

But I don't know which PCM is in your vehicle, so I don't know whether PCM Hammer or LS Droid will work at all. But they will work fine with most "locked" tunes.
I'm hoping to find out if it's locked or not, but will be away for a couple of weeks so I'll have to wait. My tuner is currently not contactable but I believe anyone with HPT can see if it's locked or not.
So, IF my pcm will work with PCM hammer, I'd be able to read and edit my current tune even if it's locked?
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Old Aug 7, 2025 | 02:11 PM
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I haven't used HPT myself, so I haven't personally tested this with an HPT-locked PCM, but there's a trick for getting PCM Hammer to work with PCMs that have corrupted flash chips, and that trick also defeats HPT's locking strategy.

If you search youtube for "tuner lock bypass" you'll find videos about it. It's tedious, but after you read the tune that way you can usually copy the tables into a non-locked stock tune and proceed from there. I say "usually" because not all versions of the PCM software are understood by Tuner Pro... but there's also a tool called Universal Patcher that works well for the odd ones.

It's a little complicated, because different people wrote different apps for the different tasks that are involved. But once you get over the initial hump, you just end up making changes in Tuner Pro and sending the changes to the PCM with PCM Hammer or LS Droid.

Last edited by NSFW; Aug 7, 2025 at 02:17 PM.
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Old Aug 7, 2025 | 09:04 PM
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Thanks NSFW.
I looked up how to bypass the lock.
Is there much risk of losing the tune or bricking my pcm in doing this?
Also, if the tune isn't locked I should be able to simply read and edit it with PCM Hammer?
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Old Aug 8, 2025 | 12:40 AM
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Low risk, and almost yes, but:
PCM Hammer is the tool for copying the firmware file from the PCM to your PC and back.
Tuner Pro is the tool for editing the file while it's on your PC.
Tuner Pro only works with certain versions of the firmware, certain "operating systems."
PCM Hammer will tell you which operating system is on the PCM, and then you look for an XDF file that gives Tuner Pro the information it needs to edit the file.

There is also a tool called Universal Patcher that can, I'm told, edit more firmware versions than Tuner Pro, but I have no experience with it.
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Old Aug 8, 2025 | 02:13 AM
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Thanks,
Wish me luck, I've just ordered the OBD Pro VX.
I'm sure I'll be back with more questions once it arrives.
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Old Aug 14, 2025 | 04:32 AM
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Ok, so I think I've successfully saved my tune file to my PC, although it only took a few seconds to read it so not really sure.
I'm now stuck though. I started looking for the correct XDF but PCM Hammer gives me OS ID 1273001, which I've worked out to be because it's been tuned with HP Tuners. Does this mean it's locked even though it seemed to read ok or is there a particular XDF I can use?

EDIT: The file I saved is 0kb so I assume I can't read the tune because of the OS ID. I'm unsure now whether I will actually be able to read it at all now.

Last edited by 2002Monaro; Aug 14, 2025 at 08:05 AM. Reason: Update
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Old Aug 15, 2025 | 06:26 AM
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Originally Posted by NSFW
Low risk, and almost yes, but:
PCM Hammer is the tool for copying the firmware file from the PCM to your PC and back.
Tuner Pro is the tool for editing the file while it's on your PC.
Tuner Pro only works with certain versions of the firmware, certain "operating systems."
PCM Hammer will tell you which operating system is on the PCM, and then you look for an XDF file that gives Tuner Pro the information it needs to edit the file.

There is also a tool called Universal Patcher that can, I'm told, edit more firmware versions than Tuner Pro, but I have no experience with it.
I've worked out that my pcm has been tuned with a custom OS using HP Tuners. From what I can tell it's not locked but hoping someone can confirm.
Does this mean that it can't be read with with PCM Hammer?
Attached Files
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Old Aug 15, 2025 | 03:08 PM
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Originally Posted by 2002Monaro
Ok, so I think I've successfully saved my tune file to my PC, although it only took a few seconds to read it so not really sure.
I'm now stuck though. I started looking for the correct XDF but PCM Hammer gives me OS ID 1273001, which I've worked out to be because it's been tuned with HP Tuners. Does this mean it's locked even though it seemed to read ok or is there a particular XDF I can use?

EDIT: The file I saved is 0kb so I assume I can't read the tune because of the OS ID. I'm unsure now whether I will actually be able to read it at all now.
I have an HPT 2bar custom OS in my 2004 GTO, and PCMhammer will look like it is reading, but only take a few seconds and give a 0KB file as well. I instead used LSdroid (which has a Windows version), and was able to read out the full file, although LSdroid did not recognize the OS number. Try yours with LSdroid and see if it will give you a readout, but be aware that you will not find a proper XDF for tuning an HPT custom OS. However, Universal Patcher may have all the tables you want to edit for it in the proper spots.
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Old Aug 15, 2025 | 10:05 PM
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Originally Posted by gametech
I have an HPT 2bar custom OS in my 2004 GTO, and PCMhammer will look like it is reading, but only take a few seconds and give a 0KB file as well. I instead used LSdroid (which has a Windows version), and was able to read out the full file, although LSdroid did not recognize the OS number. Try yours with LSdroid and see if it will give you a readout, but be aware that you will not find a proper XDF for tuning an HPT custom OS. However, Universal Patcher may have all the tables you want to edit for it in the proper spots.
Thanks.
I got it read with LS Droid and opened it in Universal Patcher.
Where is the best resource to learn how to use it?
Also, in PCM hammer it shows my pcm as P01_P59, does that mean it's P59 or is it normal to show both there?but I assume mine is P01 as my car is late 02.
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Old Aug 15, 2025 | 11:42 PM
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Originally Posted by 2002Monaro
Thanks.
I got it read with LS Droid and opened it in Universal Patcher.
Where is the best resource to learn how to use it?
Also, in PCM hammer it shows my pcm as P01_P59, does that mean it's P59 or is it normal to show both there?but I assume mine is P01 as my car is late 02.
You've got a P01 for sure.

PCM Hammer shows P01_P59 when flashing P01s and P59s because the software that flashes them is identical. The _ basically means "or."

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Old Aug 16, 2025 | 03:56 AM
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All P01 operating systems are 512 k bytes in size. All P59 operating systems are one megabyte for a size.

Rick
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Old Aug 16, 2025 | 03:50 PM
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Originally Posted by 2002Monaro
Thanks.
I got it read with LS Droid and opened it in Universal Patcher.
Where is the best resource to learn how to use it?
Also, in PCM hammer it shows my pcm as P01_P59, does that mean it's P59 or is it normal to show both there?but I assume mine is P01 as my car is late 02.
Be aware that there is no guarantee that the editable locations and descriptions in Universal Patcher will be 100% correct on an HPT custom OS. If you make a change to a table and the pcm starts doing something odd and completely unrelated, it may very well be that the table was not properly mapped out for the custom OS. If you plan to continue without access to hptuners, it may be better to revert to a factory OS that has everything properly identified in an xdf.
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Old Aug 16, 2025 | 07:05 PM
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Make a saved off and archived copy of the tune you started with out of your PCM. And then don't touch that copy again so that you can always go back to that if you screw something up in your edits with Tuner Pro or Universal Patcher. Make a separate copy of that tune especially for your efforts with Tuner Pro or Universal Patcher. Tuning is all about being methodical and deliberate when you make your changes.

Gametech's advice about finding a different operating system that has good XDF support is spot on. Sadly, I don't have any stock GM 5.7 liter tunes here that would more readily work with your 2004 Pontiac GTO but I'm sure they exist. You might also need to scale back a 6.0 liter tune or scale up a 5.3 liter tune. If you want to try these suggestions, the factory GM 12212156 OS has good XDF support for both the 5.3 liter version and the 6.0 liter version.

Edit: I will also suggest that you purchase a separate PCM for running evil tuning experiments on. There is always a chance that you could brick your primary, original PCM and then my friend, you are walking.

Rick
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