How to: Flex Fuel on C5
Racer
Joined: Apr 2019
Posts: 310
Likes: 120
From: Central PA
2024 C5of the Year Finalist - Unmodified
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Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
I could, however over on PCMhacking.net they have very extensive XDF for the -7603 OS and a "1 click patch" in tunerpro to enable flex fuel on the file. That should get you exactly what you need to get started and is actually easier and more straight forward than using HPT. I set up a few of the flex fuel tables differently than how that "patch" does it, but it at least will highlight the diffs of all of the tables that you should take a look at when moving to flex fuel. IIRC it looked like it mostly copied over values/tables from (probably) a 03 Tahoe file.
3rd Gear
Joined: Apr 2024
Posts: 3
Likes: 0
Has there ever been flex fuel enabled file made for the 12592425 OS? Unfortunately used my HPT credits before finding this and wanting to play with Flex Fuel and cannot for the life of me find a truck Flex OS of the same to merge from.
Any help greatly appreciated
Any help greatly appreciated
3rd Gear
Joined: Apr 2024
Posts: 3
Likes: 0
Thread Starter
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Send me your current or stock read or whatever file and I'll populate the FF tables for you. 12592425 calibration table layout is same as -7603.
edit: HPT does have better definitions for 7603 vs 2425. Nothing huge but they are different and 2425 is missing a few. Recently compared them in depth helping set up a friend who was on 2425. We decided to just go 7603 from the get-go.
edit: HPT does have better definitions for 7603 vs 2425. Nothing huge but they are different and 2425 is missing a few. Recently compared them in depth helping set up a friend who was on 2425. We decided to just go 7603 from the get-go.
Le Mans Master
Joined: Jun 2016
Posts: 5,466
Likes: 4,029
From: Cincinnati, OH
AFAIK, anything truck OS related you still have issues getting the fuel gauge to work right since Corvettes have dual tanks and trucks do not.
I think it's best to start with the 7603 2004 Corvette OS and simply enable FF.
I think it's best to start with the 7603 2004 Corvette OS and simply enable FF.
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
I wonder if it's not just as simple as swapping in the system segment to a truck tune to get the fuel gauge, HID, etc to work properly? But for me it was plenty simple to just use the cax file and copy/paste over all the applicable stuff from the truck tune.
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Le Mans Master
Joined: Jun 2016
Posts: 5,466
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From: Cincinnati, OH
Swapping in segments may be "easy" for some, but IMO K.I.S.S. Segment swapping also lends to more errors/issues.
Thread Starter
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
12592425 is only available for 2004 C5s, it was an update that was part of the whole column lock recall. So whether you start with the -2425 or -7603 C5 file as your base, you'll be good to go. The two calibrations even have the exact same CVN, the only change was the OS/application software logic side of things.
Le Mans Master
Joined: Jun 2016
Posts: 5,466
Likes: 4,029
From: Cincinnati, OH
@aaronc7 to the rescue again!
Your help on supplying the OS files was a life saver after the other (unrelated OS) issues I had. Thank you again!
Been enjoying that sweet corn smell since July 2023 and haven't skipped a beat!
Your help on supplying the OS files was a life saver after the other (unrelated OS) issues I had. Thank you again!
Been enjoying that sweet corn smell since July 2023 and haven't skipped a beat!
Cruising
Joined: Mar 2024
Posts: 10
Likes: 5
From: Central Ohio
I looked all over before just creating some 2004 bin files. I actually could only find an M6 file and needed the A4 so I just created it. Then I realized there is 7 pages of this thread. I will be doing a write up on my experience trying to do this soon as my pcm is ready, my gauge/sensor is installed and working, and my injectors are tested. Now I just need to install the injectors then swap the computer and continue testing. Either way hop these files can help someone. Sorry I took it away from stock for the A4, but I adjusted it to where my 02 is on and many of the adjustments were inherited and I am slowly moving things around in it. Odd thing is it runs fine and never gets to 200F even on a 7 hour drive through the Appalachians in late May. Thank you for your help and any suggestions welcomed as I also attached my hpt file. Big thank you to @aaronc7
Thread Starter
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
I looked all over before just creating some 2004 bin files. I actually could only find an M6 file and needed the A4 so I just created it. Then I realized there is 7 pages of this thread. I will be doing a write up on my experience trying to do this soon as my pcm is ready, my gauge/sensor is installed and working, and my injectors are tested. Now I just need to install the injectors then swap the computer and continue testing. Either way hop these files can help someone. Sorry I took it away from stock for the A4, but I adjusted it to where my 02 is on and many of the adjustments were inherited and I am slowly moving things around in it. Odd thing is it runs fine and never gets to 200F even on a 7 hour drive through the Appalachians in late May. Thank you for your help and any suggestions welcomed as I also attached my hpt file. Big thank you to @aaronc7
The HPT file is locked too
Cruising
Joined: Mar 2024
Posts: 10
Likes: 5
From: Central Ohio
Also does anyone have a wideband wired in on a P59? If so can it still go in through Blue 55 and read through the EGR or does it have to go another route like the AC. Which if it does then I may wait on injectors and putting E85 in until it is below 95 every day.
Le Mans Master
Joined: Jun 2016
Posts: 5,466
Likes: 4,029
From: Cincinnati, OH
You need the correct version PCM (and correct OS)
You need to swap some pins in the car harness going to the PCM
E85 FF sensor
Injectors
Proper dyno tune
May want to explain the scope of the work to whatever shop does the work.
Cruising
Joined: Mar 2024
Posts: 10
Likes: 5
From: Central Ohio
So for everyone @aaronc7 I am having issues with the EGR and FF sensor reading on any logger including Universal Patcher via OBDLink or HPT. The hardware is off a 03 FlexFuel L59 Yukon XL, thus physical provisions should be there in theory.
Here is the bin and hpt for what is most current in my car. I have tried diving pretty deep into this, and I may just grab one of the files posted in OP and try a reflash. The tune on this isn't stock, nor is it mine (previous owner did it), and I have been slowly figuring it out at the same time I never took it back to complete stock cause the engine never goes reach 200F and the way it runs is alright. Yes I know the transmissions has extra pressure on it in the current set up. Another thing that I was thinking is it could be an auto disable based on something else being disabled like the LTFT.
Here is the bin and hpt for what is most current in my car. I have tried diving pretty deep into this, and I may just grab one of the files posted in OP and try a reflash. The tune on this isn't stock, nor is it mine (previous owner did it), and I have been slowly figuring it out at the same time I never took it back to complete stock cause the engine never goes reach 200F and the way it runs is alright. Yes I know the transmissions has extra pressure on it in the current set up. Another thing that I was thinking is it could be an auto disable based on something else being disabled like the LTFT.
Thread Starter
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Quickly looked over it, and the FF stuff looks good to me, not sure why you can't see anything in the scanner.
Sometimes you have to run the car for a while for it to update, not sure if you've tried that yet.
I don't think HPT has it, but I believe there is a 2nd parameter that you can log, which is actual FF sensor hz output. This can help determine if the sensor has a hardware/wiring issue vs something with the tune. EFILive had this iirc.
Here's a file with EGR enabled at least
Sometimes you have to run the car for a while for it to update, not sure if you've tried that yet.
I don't think HPT has it, but I believe there is a 2nd parameter that you can log, which is actual FF sensor hz output. This can help determine if the sensor has a hardware/wiring issue vs something with the tune. EFILive had this iirc.
Here's a file with EGR enabled at least
Thread Starter
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Updated original post with new FF enabled files (v5) and updated XDF. The C5 base M6 file I had was actually A4 file. Not sure I downloaded the wrong file off the repository years ago, but it should be good to go now.