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

[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/conversion...ble-fixed.html

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