I'm still a complete newb at all things tuning, but have been doing a lot of research trying to figure out what I want (EFILive vs. HPTuners) etc.

I've seen that both vendors have custom operating systems. "Custom" appears to mean "not the standard GM OS". Do either of these packages provide the capability to edit the OS (i.e., the Motorola 68k machine code being executed by the PCM)? If so, do they provide a disassembler for the machine code or are you limited to just manipulating values manually with a hex editor? Any info on how to accomplish this (in particular with EFILive).

BTW, while I'm a total newb to tuning, I am an experienced software developer and have no issue playing with assembly code, even sans disassembler. The only change I'd want to make to the stock GM OS would be quite trivial. All I really want to do is replace two bytes with 4E 71 so as to not have the PCM skip over some neglected code that a few Australian GM Engineers undoubtedly worked quite hard to write.

 

i dont think you're editing HEX code at all...i thinks its all GUI via HPTuners or EFILive. Unless i am misunderstanding your question, i believe the two software designers have removed the need of learning assembly language by releasing these programs. I guess you could still do it in HEX manualy, but why?

 

99.999% of the tuning I'd be doing would be via the normal method, i.e., modifying tables using the standard GUI interface. There's just one particular trick I know of that I'd like to do that will require modifying the PCM code itself. (Not sure if it's taboo to talk directly about the actual mod here so I'm not going to mention what it is).

 

What? Just say what it is...LOL. If its taboo (which i cant imagine it is) they will remove it.

 

Lean cruise. The real Holden kind. Research suggests the only way to do it is to modify PCM code...which some people have done.

 

"lean cruise" has been discussed quite a few times here...do a search and see if its the same as what your talking about. Why the need to edit in HEX and not just use the available tables to do this?

https://www.performancetrucks.net/fo...ht=lean+cruise

 

Call Jesse at wait4me performance he is a sponsor >>>>>

 

Been looking all over here and elsewhere for info doing that exact search. The deal with lean cruise is that there is that the PCM ensures the vehicle is a Holden before executing lean cruise adjustments. The lean cruise *tables* exist in all PCMs, but they're ignored in everything but the Holdens. The way around this is apparently to find the conditional expression in the PCM operating system that performs this check and ensure that it always executes the lean cruise adjust subroutine. I've looked at a bin file for an 04 Silverado and sure enough I can find the code (courtesy of this). It's trivial to alter this code to do what I want (even without a proper machine language disassembler)... but I have no idea how to get the modified code onto the PCM.

 

I'd love to talk to him about this but understand that he doesn't perform this modification for customers out of understandable CYA concerns.

 

they also say it would cause "other issues"...i wonder what those would be? Excuse my ignorance, but what is a "Holdens" platform? How much MPG would be obtained by switching?