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Discussion Starter #1 (Edited)
Alright. I've been sitting on this for quite a few years because I had planned on making money on this mod and selling switches and full install instructions, but I've just been dragging my feet too much to make it happen. Now that there are less LBZ's on the road there is probably less demand. So, I'll get on with it.

Download:
Light Duty Elecrical manual (25-3500)
http://www.gmupfitter.com/files/media/photo/99/2006_LD_CKFullSizeElectrical.pdf

Medium Duty Electrical manual (45-5500)
http://www.gmupfitter.com/files/media/photo/198/2007_MD_Electrical.pdf

In the Light Duty manual navigate to section C-14 thru C-15 which are pages 72-73 of the PDF. Take note of pin 11 and 53 of the C2 connector. Notice they say unused.

In the Medium Duty manual navigate to C-21 thru C-22 which are pages 80-81 of the PDF. Take note of pin 11 and 53 of this C2 connector. This manual says:
C2 pin 11 (exhaust brake telltale)
C2 pin 53 (exhaust brake control)

This is the thing that got me to thinking 4 or 5 years ago. We all know that the '06 and '07 MD trucks that have the RPO of LLY are actually packing an LBZ engine with an MD tune of only 280hp, (or something close, or whatever) while the '05.5 - '07 classics have the same setup but have the LD tune of 360hp. So, knowing GM is all about recycling parts, programs, computers and whatever else, I wondered if they left the logic for the Turbine Brake from the MD programs in the LD programs. So, on a hope and a dream I wired up my switch according to the diagram of the '07 MD w/ RPO LLY. Wouldn't you know it actually worked. They did leave the logic for the exhaust brake in the LD ECMs. HOWEVER, the brake only activates while the TCC is locked up, eg. T/H mode activated. Also, with the exhaust brake activated it sends the TCM into a more aggressive down shifting map. Being, what I would refer to as, a power user of EFI Live I also attempted creating a .cax file to add tunability of the brake, but it turns out you need ALOT more knowledge of binary addresses and such that I don't know. I inquired a fellow from NZ who has made cax files before for gasser but he couldn't help me. I inquired with Ross too, but I never got very far with him. He is an extremely busy fellow. Enough history. Here it is. Im not going to tell you how to make a switch, and I'm not going to tell you what the part numbers are for the ECM pins. But I will tell you how it works and what you need to do to get it to work.

The way it works.

When C2 pin 53 is grounded this arms the exhaust brake. When all conditions are met the brake will activate. (vanes close to 100%) When the exhaust brake is actively braking pin 11 of C2 is activated sending 12v to a lamp if you choose. IT IS IMPORTANT to use an incandescent lamp and NOT an LED to act as the telltale. I originally used an LED as my lamp and it was causing some sort of fault with that subsystem making the brake engage and disengage rapidly, switched out to an incandescent lamp and it solved the problem.

Quick FAQ:

Q. Do I have to have EFI Live to make this work?
A. Nope. This is a factory loaded feature. However, EFI guys will love being about to have 5 tunes with and without the turbine brake instead of making one tune with the brake and 4 tunes without. :D;)

Q. Will this work on my LBZ/ Bosch controlled LLY?
A. Try it and find out. I have tried it on a few different OS's and an 07 classic. I haven't ever flashed the newest, so I cant say about that one.

Q. Will this work on my '04.5 to early '05 LLY?
A. Yes, but it (the ECM) doesn't use the turbine for braking. Instead, just like the MD's for that year range use a flapper in the exhaust to act as the brake. I have tested it and it does power a pin to activate a solenoid for the flapper valve on the LD trucks. Figure it out for your self. Apply the knowledge learned here to your LLY and you'll figure it out.

Q. Does this work for LMM's?
A. I have done very little messing around with it on an LMM years ago and I cant tell you which OS I did it on, but the logic in the ECM is there but doesn’t activate the brake. It does send the TCM into the same down shifting pattern as the LBZ but nothing happens with the turbo. Again mess with it your self maybe you can figure it out.

Happy braking!
 

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Interesting .. very.

I did not know that the LLY continued in the Medium Duty trucks till 07. Also interesting.!

Great post.


Theo
 

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Discussion Starter #6
Interesting .. very.

I did not know that the LLY continued in the Medium Duty trucks till 07. Also interesting.!
great post.


Theo
Well it was early 07 and RPO'd as LLY when in actuality it was really an LBZ with an MD tune. Just like in 07 there were LD classics and then there were LD GMT900s with LMM. Same concept.
 

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Now will this also work in conjuction with the factory criuse grade braking? My turbo brake from Fleece doesn't, it would be nice if this mod did.
 

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Discussion Starter #8
Yes. In TH mode when the converter is locked up and your foot is off the throttle it is engaged. To the beat of my testing I can't find any upper of lower RPM limits. It will even work in NON-TH mode when the converter is locked but it does funny stuff with the shifting and converter lockup. So, its beat to just use it in TH mode.
 

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Thanks for sharing the info. When you tested the 04-05 LLY, is it a different pin, because it looks to me like C2 pin 53 is used for EGR motor high control?
 

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Discussion Starter #11
Thanks for sharing the info. When you tested the 04-05 LLY, is it a different pin, because it looks to me like C2 pin 53 is used for EGR motor high control?
Yes, the 04.5-05 are completely different pins all together. I can't remember which ones because its been way too many years ago. But I do know that I found the info in the upfitter electrical manuals just like the lbz's. :)
 

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Discussion Starter #12
I believe it is this information plus their own progamming that Banks uses in their Speedbrake system.
Banks is a standalone controller for the turbine. It is similar in function to the Fleece turbo controller. They both intercept the sensor and control the turbine vane position based on various factors. The factory exhaust brake is a simple on/off thing.
 

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Ok, thanks. I'll see of i can find it in that manual.

One last question if you don't mind- on the LD LLY trucks, is the solenoid that is actuated by this switch already part of the exhaust system, or does it require an add on valve?
 

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Discussion Starter #14
Ok, thanks. I'll see of i can find it in that manual.

One last question if you don't mind- on the LD LLY trucks, is the solenoid that is actuated by this switch already part of the exhaust system, or does it require an add on valve?
The only thing that the factory function does (from memory) is send +12v from one of the ecm pins to activate a relay that activates a selonoid that closes the exhaust restrictor valve. All of which is add-on by you, but a factory option for the MD Trucks. So, in theory you should be able to order all the factory parts from the MD and add them to your LD. Or, do a custom setup.
 

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Impressed

Thanks for the great info. I hope to do this before going from MN to AZ this winter. Can I as the size of the bulb (or wattage) that you used for an indicator?
Do you know if the arming switch can be a momentary switch to arm and the ecm then stays armed until T/H is switched off or throttle is applied?
:cool:
 

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I just wired mine up last night and it works. Thank you bballer182 I have been having trouble with my fleece turbo brake throwing codes.
 

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Does anyone have any thoughts on what might happen if this wire is activated on a LLY(LBZ) with a manual transmission?
As I recall the LLY model used in '05 with the manual transmission were the older, '04 leftovers that still had fixed vane turbo's. It was explained to me at the dealer when I was looking at '05 models, and I asked why there were two different power ratings with the Duramax's. Since '05 was the last year for the manual transmission they didn't bother spending money to fit them to the newer engine. So with that being said I don't believe it will work.
 

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Discussion Starter #19
As I recall the LLY model used in '05 with the manual transmission were the older, '04 leftovers that still had fixed vane turbo's. It was explained to me at the dealer when I was looking at '05 models, and I asked why there were two different power ratings with the Duramax's. Since '05 was the last year for the manual transmission they didn't bother spending money to fit them to the newer engine. So with that being said I don't believe it will work.
That's not true. The salesman told you lies because you asked a question he didn't know the answer to. Historically modern diesels have down rated HP and tq ratings when coupled with manual transmissions. This holds true with the Dmax line. And there actually is in fact a few '06 dmaxs that had manual transmissions. They might as well be unicorns, but they do exist.
 

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Discussion Starter #20
Thanks for the great info. I hope to do this before going from MN to AZ this winter. Can I as the size of the bulb (or wattage) that you used for an indicator?
Do you know if the arming switch can be a momentary switch to arm and the ecm then stays armed until T/H is switched off or throttle is applied?
:cool:
The switch cannot me monetary. Its either On or Off. (Unless of course you feel like holding the momentary button the entire duration that you wish to use the brake.)
 
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