Medium Duty CAN bus Protocol

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
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I thought I heard that they were using LML ecms?

There 1st ones looked like a custom ECM, but they started producing them with LMM engines back in 07 well before the LML. Didn't know if they had changed when GM went to the LML or not. I don't see any orange loom for the injector wiring on there new engines, so who knows.
 

kidturbo

Piston Tester
Jul 21, 2010
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Last time I spoke with them, they were using a straight off the line LMM VAN engine, adding their own water cooled exhaust, charge cooler. and some small parts. The reset of those pieces are Mercruiser. They ran a custom tuned LMM ECM (360 - 500hp at crankshaft), paint it white, and slap a $35k sticker on it. Not bad, when the US Gov or NATO is your intended customer.

For the marine tuning side, I've got that part down pat. Saved 20 some revisions files over 4yrs, on top of the purchased DSP5 LLY starter tune. Lot of tweaks like torque limiting to protect the outdrive, major idle related changes, and drive ability remapping cause boats never coast. 300 plus trouble free engine hours later, I'd call it bullet proof. Don't know any floating Duramax platforms even close to that number yet.

It's not hard to bolt one up in a boat. Making it run strong, and last like you'd expect a diesel is where I evaporated 30k in a year. lol... But the LMM is a great starting point now, vs the LLY at least. And I feel it's the go to platform if we can make an affordable swap package. There is other changes required like drive gearing and new props that might cost ya as much as the engine swap.

I owe a big shout out to guys like Fingers who helped explain the weak points, and Curtis who blew up many motors to prove ya can't spin one 5000R's in a boat all day. Lot of comments were taken to heart, so gotta give credit where due. Reason I always try to help out the next guy who wants to tackle a crazy swap.
 
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TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
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BTW, I didnt mean to slight kidturbo earlier. Glad he is here talking electronics, and sounds like a heck of a smart guy.
Would be pretty darn cool if he and Ben come up with some new gadget or problem fix with your brainstorming.
 

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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Im not doing anything "special" or rocket-science stuff. Seriously. This is nothing but entry level electrical stuff that anyone with the internet and some reading time can learn and figure out.

I appreciate the compliments, but really Im not creating anything new, Im not inventing anything...im just using readily available information on the internet to figure out what someone much much smarter than me has already figured out.

You want to talk real smarts, guys who are actually genius and taking the Duramax world to the next level, talk to the guys like SoCal/Guy, Kory, Fingers, Mike L, EFILive, etc. They are the ones doing the really crazy things.

Like I said, anyone can figure out the elementary stuff Im doing. Its just that no one bothers because there isnt a huge market or much money in the niche part of the industry. How many engine parts or EFILive tunes do you think are sold, for every ONE "LML standalone GMLAN theft system spoofer" module? Honestly, I do this stuff because I get a kick out of it, and its the only way I know how to make a little money. If there was something less interesting but more profitable, I'd never do this stuff again. Truck gizmos are cool and *gee whiz* but they only barely pay the bills. :(
 
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kidturbo

Piston Tester
Jul 21, 2010
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I verified a couple interesting points over the weekend hacking around on a LMM.

1. The BCM is the gateway (translator) between high speed bus and the low speed GMLAN. It's also a gateway between the DLC16 connector and high speed bus.

2. High speed bus from engine harness connects to the BCM on plug X3. Verified this by continuity, some GM docs show X2 as the plug, so ???

3. Engine will not start with BCM X3 plug disconnected (as suspected). However it will continue to run fine after the X3 is removed, isolating the ECM/TCM harness. Dash goes dead that point.

4. EDITED -- Finally got connected to the correct ECM/TCM bus, there is actually 2 GMLAN high bus connections on that X3 plug.

Soon as I EFI tune truck I'll turn off VATS and test engine starting again with the BCM disconnected. I did run across a good description of the BCM plugs pinout at:
http://www.carmodder.com/viewtopic.php?t=14534&f=253

-K
 
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kidturbo

Piston Tester
Jul 21, 2010
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Tuned that friends LMM truck today and tested our VATS options. Worked much as I suspected, with VATS set to off, any key that turns starts it. However not when BCM is disconnected. So I called up the guys I know had done it for the answers.

GM tech buddy said up to 2013 you can disable VATS with EFIlive and scrap the BCM. Newer than that your gonna need couple other modules attached. Or as Ben stated above, a way to fake the CAN security data to the ECM.

LMM in my friends boat, they simply disabled VATS and keyed 12v hot and a fresh ground to the powertrain relay. Always starts and runs just fine he said. Also running a 6 speed Allison in that boat. Been a good bit more work making it happy vs powering the ECM.

Hope that helps someone. Back to my 1's & 0's research for now.. :thumb:
 

duratothemax

<--- slippery roads
Aug 28, 2006
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Wyoming
GM tech buddy said up to 2013 you can disable VATS with EFIlive and scrap the BCM.

Unfortunately, he is incorrect...or he is guessing and never actually tried it.

Ive tried every single LML OS, 2011-2015 in a standalone setup with the VATS set to DISABLE.

NONE of them will start just by giving the ECM ignition power and jumping the starter. Ive tried this personally. Doesnt work. :(

Ben
 

kidturbo

Piston Tester
Jul 21, 2010
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His statement was only that in 2013 the ability to swap modules between vehicles went away in everything including trucks. Like taking an ECM or BCM out of one truck, changing the VIN, to plug it right into another one. We never specifically discussed the LML, only the LMM in medium duty setups with VATS, along with some other gas vehicles. He recalled GM changed the way modules were replaced around this time, but medium duty was long done... I was however able to easily bypass security on a LMM, so that old view that only up to LBZ's works stand alone is busted.

I was also able to log a good bit of high speed GMLAN engine / trans data over the weekend. Including Torque app and Edge gauge pids, EFIlive's pids, plus read / write programming commands to the ECM. Ran out of time to see what the SnapOn tool could show me. But with access to an LML truck for a few days, pretty much guarantee I could bypass the powertrain security with a simple network connection. So making one run stand alone shouldn't be a big deal.

Actually read a related article a guy wrote on how hijack the rolling key fob codes and on new GM vehicles. He demonstrated how to unlock or start one after the owner attempted to lock the doors while walking away. Pretty sneaky little trick.

Also have this pre-ban Edge CS Full Race tuner pictured below on the steering wheel if any out there is looking for those. Owner doesn't need it after the EFI upgrade. PM me for details about it. I'll post up some wiring points I found too regarding the LMM communications buses later on.
 

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Dogface1SG

New member
Oct 30, 2016
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Ohio
kidturbo or duratothemax

I am trying to get the info to setup balance rate and fuel rate on a 2006 LBZ.

Could this method be used to sniff out what I need?

Read through the entire post, quite impressive what you have done. New to it all so trying to absorb it.
 

Dogface1SG

New member
Oct 30, 2016
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Ohio
Btw

Just got my ScangaugeII back from being updated. It does read Balance rate but not fuel. It was a free upgrade for the LBZ. Sent it to them via USPS and was mailed back no charge. Heck of a deal.

I really want to get it working in Torque as with the Scanguage, you can only see 4 at a time.
 

kidturbo

Piston Tester
Jul 21, 2010
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I had a spare LBZ ECU here for testing, but sent it out to a friend in CA to play with. Your on the right path, just need to sniff the packets from another tool that can read bal rates, then create those PID's in Torque.

Soon as I get my V2 back from my partner later in the week I'll capture that command from one of the LMM ECU's I have here now. Believe it's same between LBZ-LMM.
 

Dogface1SG

New member
Oct 30, 2016
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Ohio
Thanks for the reply

That is what I thought. I can get them from my Scanguage by sniffing.

Now I need to purchase a setup like you used, borrow a TechII to get the others that I would like.

Can this all be done on the truck using the OBDII port and a Y cable? I have been looking into them as well.
 

Dogface1SG

New member
Oct 30, 2016
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Ohio
One of the other things I would like to find a way to do is reset the engine oil life and fuel filter life.

I have the work truck config, no steering wheel buttons. Do you know if that would be possible as well.

Just learning Torque and digging deep into CAN PID research
 

Dogface1SG

New member
Oct 30, 2016
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0
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Ohio
It should send the same commands when I do the brake pedal or accelerator pedal combination I would think.

The updated scangaugeII has the engine oil life remaining but doesn't reset it. I plan on that as well with the fuel filter life. I can make a fuel filter life very easily as it is just every 10000 miles.

Thanks again for the Input
 
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ArrBee

New member
Aug 12, 2010
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Hmmm ...for some ODD reason I am thinking that fuel filter changes should be based on the volume of fuel that has passed through the filter.
While the miles traveled is related, it is quite indirect.
So many factors are involved; load, traffic, terrain, driving style, trip distances, etc those can cause quite large differences in fuel volume used per distance traveled.

I thought GM based service intervals partly on the number of cold starts, but that may be for oil changes.
 
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