Last ditch...ANY way to support flex fuel on 2002 COS

[DURAtotheMAX]

The van OS isn't setup to read in and use the pressure switch, so basically the van OS is out. The truck OS/ECM will work with the pressure switch, but is technically only databus controlled. If you wire in discrete inputs to the truck- the ECM simply doesn't have the hardware to signal anything.

So the trick is to use the truck OS on a van PCM. It will accept discrete inputs, read the pressure switch, and cycle fans.

Interesting!! So even though the truck OS is setup from the factory for analog pressure sensor and databus controlled AC, it still monitors the discrete trigger input anyway? And its actually the hardware that is different? IE, the truck PCM doesnt have the AC request input pin wired to to the processor internally?

I wonder if the Duramax's are setup the same way? (kodiak/van uses discrete input, pickup truck uses databus)

All LS1b cars use variable displacement compressors. Trucks use fixed displacement. Look it up.

http://ls1tech.com/forums/conversion...ble-fixed.html

http://ls1tech.com/forums/conversion...mpressors.html

Ahh ok, interesting....I was not aware of that...I work with pretty much all truck stuff, so I ASSumed incorrectly. Thanks for the correction.

Ben

[RADustin]

Interesting!! So even though the truck OS is setup from the factory for analog pressure sensor and databus controlled AC, it still monitors the discrete trigger input anyway? And its actually the hardware that is different? IE, the truck PCM doesnt have the AC request input pin wired to to the processor internally?

I wonder if the Duramax's are setup the same way? (kodiak/van uses discrete input, pickup truck uses databus)



Ahh ok, interesting....I was not aware of that...I work with pretty much all truck stuff, so I ASSumed incorrectly. Thanks for the correction.

Ben

Please don't confuse my verbiage for being harsh in my above post. Rereading it I understand how I could have come off a little side ways!

That is correct about the ECU. It's just a hardware deal.


It is possible the diesels are similar. Doesn't the LB7s use an 0411 style ECM?

[turbo_bu]

couple things going on. For 1mb...

I know nothing about a/c over databus as I focus on swaps into older vehicles.

But- say you want the PCM to run the fans when the a/c kicks on. If you run the standard van setup(van ecm, van OS, and van wiring) with discrete inputs and simple binary switch, the fans will never work. You have to have the pressure switch and have it functioning in the OS for the fans to be kicked on.

The van OS isn't setup to read in and use the pressure switch, so basically the van OS is out. The truck OS/ECM will work with the pressure switch, but is technically only databus controlled. If you wire in discrete inputs to the truck- the ECM simply doesn't have the hardware to signal anything.

So the trick is to use the truck OS on a van PCM. It will accept discrete inputs, read the pressure switch, and cycle fans.


All LS1b cars use variable displacement compressors. Trucks use fixed displacement. Look it up.

http://ls1tech.com/forums/conversion...ble-fixed.html

http://ls1tech.com/forums/conversion...mpressors.html

Just to clarify, when you use a Van 1 MB PCM with a Truck OS, are you "converting" the truck OS to a DBC?

[RADustin]

Just to clarify, when you use a Van 1 MB PCM with a Truck OS, are you "converting" the truck OS to a DBC?

typically I always use DBW in my swaps. I like the ease of cruise control and lack of a physical cable. Also I like to use the TB to limit RPM instead of fuel or spark as many times it is FI.

You could use either. The van ecm will support DBW or DBC, it is the universal 1mb. For this last swap when I figured the difference in ECM hardware, I wanted DBW. I put the entire truck image on the van ECM.

[GMPX]

It is possible the diesels are similar. Doesn't the LB7s use an 0411 style ECM?

It is funny you say that, yes internally there is many similarities but the code in the LB7 was done by Isuzu, not GM. In fact many PCM's of that era are of similar build internally, the 3.8L V6, the 4 Cyl engines, the weird V6 PCM on the Isuzu Trooper, but they all run very different software that has nothing in common.

I think it was mentioned in this thread that some 1Mb PCM's are missing parts internally (driver outputs), I don't know what Service Number is the one with the lot but keep this in mind.

[RADustin]

is there no way to recompile the source for 512k ecus for a 1mb?

that would be pretty sweet.

[joecar]

is there no way to recompile the source for 512k ecus for a 1mb?

that would be pretty sweet.

He doesn't have the source... (he reverse engineered the 512K and 1M PCM's... that is not the source, it is what the binary code does in terms of assembly language mnemonics).

[RADustin]

I'm pretty sure once you have the assembly it could be recompiled for a different chip. No?

[RADustin]

Maybe hardware would screw it up? But assembly could be changed to allow for different hardware??

I'm reaching I know.

[joecar]

I'm pretty sure once you have the assembly it could be recompiled for a different chip. No?

Not necessarily...

to start with, the different PCM's would have different addresses for the various devices...

the actual source code would have named constants for the device addresses, and if the source code supported various PCM's then it would adjust the named constant addresses to suit the hardware it was being compiled for;

also, the various devices might have different behavior across the different PCM's.