LLY Ficm

[2004LB7]

Me thinks a few mosfets and some resistors is all that is needed to invert the signal. One could open up the LB7 FICM and install them on the control lines to make it an LLY compatible FICM. Or if you're willing, cut the wires in the harness and install them before the FICM

 

[2004LB7]

Ok, clarification needed. Is it the injector control or the crank signal that is inverted. Because reading through it I thought you where saying it's the injector control. But now looking at the screen capture of the crank signal makes me think that is what is inverted. Inverting the crank signal would be so easy with a single set of mosfets on one wire like the image above. But the injector control will have to have eight of them

 

[kidturbo]

Ok, clarification needed. Is it the injector control or the crank signal that is inverted. Because reading through it I thought you where saying it's the injector control. But now looking at the screen capture of the crank signal makes me think that is what is inverted. Inverting the crank signal would be so easy with a single set of mosfets on one wire like the image above. But the injector control will have to have eight of them

I looked at all of the captures, and it's inverted compared to the LLY. See below.

Sorry, was just sharing how that crank signal looked at startup. It could have been setting with a tooth positioned just right, to pull it high, but I thought it was interesting.

LB7 Control Line - No Crank Signal Connected


LLY Control Line

 

[kidturbo]

Me thinks a few mosfets and some resistors is all that is needed to invert the signal. One could open up the LB7 FICM and install them on the control lines to make it an LLY compatible FICM. Or if you're willing, cut the wires in the harness and install them before the FICM

View attachment 117294

I think that's a reasonable approach.
Build it on breadboard with some pigtails, and then you could test this inline at the FICM connector on a truck or bench just to see if it fires injectors.
On a new board build, it wouldn't be hard to make it an internal switchable option.

 

[2004LB7]

I looked at all of the captures, and it's inverted compared to the LLY. See below.

Sorry, was just sharing how that crank signal looked at startup. It could have been setting with a tooth positioned just right, to pull it high, but I thought it was interesting.

LB7 Control Line - No Crank Signal Connected
View attachment 117295

LLY Control Line
View attachment 117296

Ok. That makes sense. Crank signal is the same. Control is inverted

I think that's a reasonable approach.
Build it on breadboard with some pigtails, and then you could test this inline at the FICM connector on a truck or bench just to see if it fires injectors.
On a new board build, it wouldn't be hard to make it an internal switchable option.

Exactly. Some dip switches to swap between LLY and LB7

 

[1FastBrick]

Is what I see so far. Exact opposite of LLY. Kinda throws a wrench in the modify a single signal wire idea...

Just confirmed the crank signal does the same. But since we don't have a key-off to cranking save from the LLY, I can't be certain if those part are the same. But here is example.

FICM Pin 94 Key Off zero volts, to key on.



Key On to Cranking



Cranking to Running

We could have if someone said something...

 

[darkness]

So just happened upon an engine/tranny out of a Kodiak. 2005 complete wiring harness, ecm, looks like the FICeM is still there. Misc other parts with it for $2500. Should I pick this up for research? Says the truck was rear ended but the front is fine.

Well, no go on that. Motor looked like it had been in a fire and the FICeM had a freakin hole in the lid. Plus it has been sitting outside for I’m sure 4 years. Looked like it came from the rust belt. Ok, back to your regular scheduled program.

 

[1FastBrick]

Well, no go on that. Motor looked like it had been in a fire and the FICeM had a freakin hole in the lid. Plus it has been sitting outside for I’m sure 4 years. Looked like it came from the rust belt. Ok, back to your regular scheduled program.

So typical junk for sale that someone thinks they can get alot of money for...

 

[2004LB7]

Well, no go on that. Motor looked like it had been in a fire and the FICeM had a freakin hole in the lid. Plus it has been sitting outside for I’m sure 4 years. Looked like it came from the rust belt. Ok, back to your regular scheduled program.

Was the hole for the pressure balance plug? Or another?

 

[kidturbo]

Did some digging around tonight for the two Bosch connectors used on the FICM's. Found there is still several thousand of the female "harness side' available in the market. Going price, about $90 for the bigger one without pins or locks.

However as I've noted on all the other Bosch built modules, there is no matching male connectors listed. Gonna have to break out a 3D printer. I did find and DL some decent technical drawings for the female harness side. So if anyone on here is a CAD guru with some spare time, will be something to work on that will certainly come in handy going forward.

 

[darkness]

Was the hole for the pressure balance plug? Or another?

You know, it could’ve been. I forgot about that. It wasn’t a clean hole though but the plug was gone.

 

[kidturbo]

Setting here getting ready to cannibalize this medium duty LB7 harness, I have to say, I like the simplicity of it for chassis swaps..

Fuse block is nice and "clean" compared to others.

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[kidturbo]

Ok here we now have a stand alone FICM harness.

Will clean it up with some soap, then wire up the power, ground, and canbus to see what it has to say for itself.

I can tell ya for certain now the crank signal wire is important. They added this "yellowish top of picture" ground shielded section where the LT BL pin 94 wire runs thru the harness over to the bail connector. I imagine they did it because the driver side injector bank wires are also in that section of harness. But it sure looks like an afterthought.

Also noted that even though the crank and cam trigger wires are in that same harness and bail connector, yet they didn't Tee into signal directly from the crank pickup. Seems it's an ECM replicated signal.

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[1FastBrick]

What purpose would that serve? Is it to make sure you don't get electrical interference?

 

[kidturbo]

What purpose would that serve? Is it to make sure you don't get electrical interference?

Yes.
The Crank and Cam signal leads are fully shielded from sensor end to the bail connector for that reason. Basically just 3 wires wrapped in a foil, that is block grounded. The high voltage injector wires will interfere with a low voltage crank signal if ran together.

Also if you don't mount the bail connectors as per OEM design to the valve cover, and that crank signal wires get to close to an injector, they will misfire at high RPM. Mark and I discovered this first hand on the dyno some years back. Pretty certain there is a whole page dedicated to that issue we discovered under the Twins thread..

 

[kidturbo]

Ok just got things wired up on the bench, and say BT needs to check his math.

The Isuzu unit looks to be a brick, while the other one fired right up. The Cat was correct for those wondering... LOL

This one is squawking some data, however it's Proprietary PGNs. Which for those not familiar, under J1939 Protocol, things like tach signal on engine have a specific ID / PGN and byte order to the data so everything connected knows thats RPM signal.

This unit is sending PGN 65280 and 65281 with a couple active bytes of data. Which under the J1939 PGN list, those say "Proprietary" no further data. So basically, it's anyones guess what it's trying to convey.. But I bet it's speaking to the ECM..

I'll keep hacking around and see if it responds to some common messages before adding the ECM to the conversation.

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[1FastBrick]

Holly Hack batman.... That software look's similar to another program I was playing with.

This is the LB7 unit?

 

[2004LB7]

Looks like an LB7 FICM to me

 

[kidturbo]

Holly Hack batman.... That software look's similar to another program I was playing with.

This is the LB7 unit?

Yeah I don't have a LLY FICM handy.
The software is just a simple J1939 monitor written for a cheap CANbus board I purchased long ago.

 

[kidturbo]

Ok after an hour, it's still working. That's pretty good for me..

Tossed everything at it diagnostically I can do by hand with sub $100 tools, and can say fairly certain that it doesn't conform to J1939 protocol by any way besides it registers correctly on the bus at start up.

Doesn't seem to respond to basic requests for DM2 trouble codes, and doesn't broadcast any DM1 codes, yet setting here with every major circuit in an Open state. I even sent it basic engine / transmission protocol packets like RPM, Load, Temps, Pressure, Gear, and noting changed in it's streaming 2-line of data structures. Leaning towards that dumb box theory again.

However I did notice that PGN 65280 Byte 0 is always 0x80. And from sniffing other HS GMLAN packets, 0x80 in Byte 0 usually equals an Open Circuit or unhappy parameter if I recall. So might be catching on to the GM engineers Proprietary PGN structure.

The Second PGN 65281, has just one bit flashing on and off every 500ms like a heartbeat signal or something. That's as it has to say so far.

Any LB7 gurus left out there with winos dissected bin files, it would be helpful to know if anything relevant matches up to this simple data structure. I'm guessing it's simple diagnostics inputs for the ECM to use.