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

[GMCtrk]

I really want to run the ethanol sensor and have the PCM control fueling based on composition.

I see posts here and there about people running hacked tunes to get this done and I am specifically referring to using a COS (I am boosted). OS for the 2002 Tahoe L59.

Only other options are to repin to an 03+ pcm

or

HPtuners.

And I don't want to do either of those.

[GMPX]

GM released one 'real' Flex Fuel OS for the 512K PCM (which is what your 2002) is, problem is it is about 99% full so there is no space for custom OS additions. We didn't support every 2003+ PCM OS for a custom OS conversion, just because of the amount of work involved for each one, again they did do some specific OS's for Flex Fuel in 2003+ but I can't recall if there is a COS for them.
Not sure how HPTuners is going to help you either unless they have a COS for the 512K PCM running the factory Flex Fuel OS.

[GMCtrk]

Thanks for the reply. At least know I know why there is no COS for that OS. I was always under the assumption it was just wasn't done and there was no care to do it, rather than an actual hard limit on the PCM.

To my knowledge, HPTuners does have a COS that allows for real flex fuel on 2002.

[Lextech]

You don't need to repin for the 1mb PCM. Just delete codes P0135 and P0155 for the O2 heaters and change your red connector plastics to green. Find a 1mb calibration you want to start with and have fun.

Jeff

[RADustin]

You don't need to repin for the 1mb PCM. Just delete codes P0135 and P0155 for the O2 heaters and change your red connector plastics to green. Find a 1mb calibration you want to start with and have fun.

Jeff

when doing this, does the heaters not function? what are the differences?

[Lextech]

When doing this, do the heaters not function? What are the differences?
The heaters still function. On "Most" of the earlier trucks the heaters get their ground/low reference from the harness to a ground point and not back to the PCM.

Jeff

[RADustin]

so the 1mb wants to supply the low reference where the 512K just uses the harness.

That's neat. I didn't realize it was so easy to swap to 1mb.

[Lextech]

Remember if you want to run DBW then you will need the matching 1mb DBW components. If you are DBC then you will need a 1mb PCM that has the IAC drivers in it.

Jeff

[RADustin]

If I wanted to go backwards from 1mb to 512 so that I had a COS3/5 available...and I was DBW, I would need to change throttle body or just pedal and tac? Canbus wouldn't matter as this would be in a swapped vehicle.

[Lextech]

The 2002 T/B is not compatible with the 1mb PCMs. There may be a guru somewhere who can make it work but as far as I know---It won't.

Jeff

[RADustin]

got it.

Thanks!

edit- I assume the opposite as well? 03+ TB will not work on 512?

[Lextech]

Correct---for DBW.

Jeff

[greasess]

I would love to have a 3 bar COS with flex on a 0411. I know HPT has a 2 bar OS with flex. As e85 becomes more available I think the demand for flex capability will increase. There are 4 fill stations in my area that have e85 now. More and more people want this feature all the time.

[RADustin]

Although I appreciate everything EFILive does for us- I think more and more HPT will be the way to go for COS. I know I am purchasing it just for that reason for 1mb.

[GMCtrk]

Remember if you want to run DBW then you will need the matching 1mb DBW components. If you are DBC then you will need a 1mb PCM that has the IAC drivers in it.

Jeff

It's DBC.

In that case, are the drivers specific to the PCM itself, or is it just part of the tune? I'm sure there's a G-van 1mb tune out there available (they had cable TB to my knowledge).

[RADustin]

anytime you use a 1mb, its best to use a van ecm. It is the 0411 of the 1mb world and is fully populated. The a/c circuits are setup both ways as well for variable or fixed displacement compressors.

[DURAtotheMAX]

I'm sure there's a G-van 1mb tune out there available (they had cable TB to my knowledge).

Keep in mind some vans had drive by cable, some were drive by wire. All 2003 vans are drive by cable. Starting in 2004, Stabilitrak (ESC/TCS) became available in some vans (04-05 was 15-passenger vans only, I think 06 they added it to the shorter wheelbase passenger vans, and didnt add it to the cargo vans until 09 or something), so obviously a van with traction control/stability control is going to be drive by wire.

So if you're grabbing a van PCM or calibration for your drive by cable engine, make sure its from a non-ESC van... The RPO for stabilitrak is "JL4", so if you arent sure, check the VIN for that RPO.

Ben

[DURAtotheMAX]

The a/c circuits are setup both ways as well for variable or fixed displacement compressors.

As far as I know, no GM vehicle using an LSx small block has ever used a variable displacement compressor to date. They are all typical fixed displacement AC compressors with an on/off clutch.

The differences in AC control is some vehicle platforms used a discrete input to the PCM to request AC (IE, vehicles with a basic HVAC system), thats just a simple "apply +12v to this pin on the ECM, and it will then engage the compressor clutch. This AC request signal wire first runs through a high pressure cutout switch, because otherwise the PCM would never disengage the AC compressor.

And then other vehicles used an analog 3-wire pressure sensor that the PCM monitors directly, and the AC request command is sent to the PCM over the data bus. So basically, the HVAC module commands the PCM over the data bus "I want the AC on"...and the PCM then reads the pressure sensor, and cycles the compressor on/off based on that.

All 2003+ pickup trucks and SUV's are 3-wire sensor, AC request over data bus setups. All 03-09 Kodiaks, and all 2003-2007 (pre-E38/GMLAN era) G-vans are all "discrete input".

All 2002 and older pickup trucks/SUV's are discrete input.

So if you have a 99-02 truck/SUV that is drive by cable, and you want to use a 1mb PCM, use a 1mb non-traction-control van calibration..

As far as I know, there is no drive-by-cable 1mb calibration that has AC request over data bus...

Ben

[RADustin]

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/conversions-hybrids/1017290-converting-your-ac-compressor-variable-fixed.html

http://ls1tech.com/forums/conversions-hybrids/1498442-fixed-variable-displacement-c-compressors.html

[1FastBrick]

GM released one 'real' Flex Fuel OS for the 512K PCM (which is what your 2002) is, problem is it is about 99% full so there is no space for custom OS additions. We didn't support every 2003+ PCM OS for a custom OS conversion, just because of the amount of work involved for each one, again they did do some specific OS's for Flex Fuel in 2003+ but I can't recall if there is a COS for them.
Not sure how HPTuners is going to help you either unless they have a COS for the 512K PCM running the factory Flex Fuel OS.


HPT has a COS for a 2 bar as mentioned.

If possible, a 3 Bar COS for the 02 flex fuel would great!!! We would rather use the tools we have Vs. buying something else.

[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/conversions-hybrids/1017290-converting-your-ac-compressor-variable-fixed.html

http://ls1tech.com/forums/conversions-hybrids/1498442-fixed-variable-displacement-c-compressors.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. :D

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. :D

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/conversions-hybrids/1017290-converting-your-ac-compressor-variable-fixed.html

http://ls1tech.com/forums/conversions-hybrids/1498442-fixed-variable-displacement-c-compressors.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.

[joecar]

I know this: if it were simple to do, I'm sure Ross and Paul (and pretty much most people) would have done that first.

[GMPX]

is there no way to recompile the source for 512k ecus for a 1mb?
We don't, (in fact nobody) recompiles the full PCM software except GM. All that is done on a custom OS is little routines are added here and there (easier said than done of course).