C5 Corvette Flex Fuel with P59 pcm conversion
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Sounds like it's not worth worrying about running the wires to the PCM then and just disable those codes.
Just going to be moving the alternator pin and adding pin for flex fuel sensor...pretty simple for us with the blue/red connectors.
Some of the P59 ecu info you have posted on github helped me immensely map out some of the flex fuel tables, so thank you for that!
Acct Suspended APR 2026 by request
Joined: Dec 2010
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2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
I'm looking to tackle this very soon.
Regarding the O2 sensor grounding. P01 grounds the heater to chassis. P59 uses a heater ground that is grounded to the PCM.
Option 1 would be to just not change any wiring and disable any codes you get associated...seems like this is what most do, not a big deal.
Option 2: Run the ground wires from the front O2 sensor to the appropriate heater grounds into the P59 PCM.
Is there any advantage to option 2-- better O2 accuracy/control? Anyone tried it out?
Regarding the O2 sensor grounding. P01 grounds the heater to chassis. P59 uses a heater ground that is grounded to the PCM.
Option 1 would be to just not change any wiring and disable any codes you get associated...seems like this is what most do, not a big deal.
Option 2: Run the ground wires from the front O2 sensor to the appropriate heater grounds into the P59 PCM.
Is there any advantage to option 2-- better O2 accuracy/control? Anyone tried it out?
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Thanks for the link! I'm sorta familiar with grounding stuff. It was a big topic of discussion when I was running megasquirt on my old turbo miata. Specifically how to wire the wideband to minimize the ground offset error and things like that. TLDR-- ground it to same place that the ECU is grounded. On the wideband I run now, I actually do account for ground voltage offset, I compared the digital output of the gauge to the analog signal that is wired to my gauge and adjusted the linear equation so they matched perfectly--or as close as I could get it across the normal AFR range.
Anyways back to this, it was my understanding that the sensors have 4 wires-- 12V powah, Signal, Signal ground and heater ground. So I THINK the actual signal ground is already wired back to the PCM for best possible accuracy etc. I'm not sure heater ground going back to PCM has any advantages other than simply allowing it to better monitor the status and pop a check engine light should something go out of limits.
Either way I don't think I'm gonna mess with it during my first trial run of all this stuff. Maybe a project for later.
Anyways back to this, it was my understanding that the sensors have 4 wires-- 12V powah, Signal, Signal ground and heater ground. So I THINK the actual signal ground is already wired back to the PCM for best possible accuracy etc. I'm not sure heater ground going back to PCM has any advantages other than simply allowing it to better monitor the status and pop a check engine light should something go out of limits.
Either way I don't think I'm gonna mess with it during my first trial run of all this stuff. Maybe a project for later.
Cruising
Joined: May 2018
Posts: 12
Likes: 7
From: SoCal
Sort of, but not exactly.
Sort of, but not exactly.
Read this:
https://www.facebook.com/ShorTuning/...33255476687762
There are hidden parameters in the '04 C5 OS that need to be modified, but they are not shown in the HP Tuners or EFI Live GUI. Professional tuners know what and where they are, but it is a trade secret.
Sort of, but not exactly.
Read this:
https://www.facebook.com/ShorTuning/...33255476687762
There are hidden parameters in the '04 C5 OS that need to be modified, but they are not shown in the HP Tuners or EFI Live GUI. Professional tuners know what and where they are, but it is a trade secret.
The above reference to "hidden tables", "binary hacks", etc. may be my issue.
Is there a way for me to do this myself, or do I need to pay a "Professional Tuner" to make the needed changes?
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
I have a 2004 Z06 with the P59 OS ... it has Flex Fuel parameters but enabling them with a sensor hooked to Blue 56 on PCM does nothing. I do see a 5V reference coming out of the PCM on the Blue Pin 56 not sure that makes a difference. Also, used the Continental Flex Sensor which has slightly different pin wiring than stock.
The above reference to "hidden tables", "binary hacks", etc. may be my issue.
Is there a way for me to do this myself, or do I need to pay a "Professional Tuner" to make the needed changes?
The above reference to "hidden tables", "binary hacks", etc. may be my issue.
Is there a way for me to do this myself, or do I need to pay a "Professional Tuner" to make the needed changes?
https://www.corvetteforum.com/forums...uel-on-c5.html
Cruising
Joined: May 2018
Posts: 12
Likes: 7
From: SoCal
I use HP Tuners for tuning [Beta 4.7.694] and have used an E85 Tune file for comparison and to copy in the "basic" parameters, including enabling the Flex Fuel. I also have a GM Tech 2 but it is not picking up the Alcohol PID, so far.
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Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
For example, even changing the option to "FF enable", there's still settings that define, ethanol sensor Hz at 0% composition, composition slope, etc. Which are not viewable by default and zeroed out in the C5 tune file.
I use EFIlive or else it would be a simple copy/paste fix for you.
Cruising
Joined: May 2018
Posts: 12
Likes: 7
From: SoCal
I have never did a table definition ... let me see if I can figure it out in HP Tuners. If I can adapt your table def's, then it should be a done deal. I'll comment back on my progress/success. Thank you.
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
I'd love to have the info and tune files available for HPT, but since I don't have the software/cable I can't really test it. And from my understanding, it's a $100 fee or something for hptuners to enable custom table definitions...so again, another hurdle for me.
I was just going thru my files and I think I might have a good starting point XDF for you. Might be missing a few of the tables I defined in my EFI file, but I think it's about 80-90 percent complete and has enough table definitions to get the job done. Shoot me a PM and I can send it over.
I was just going thru my files and I think I might have a good starting point XDF for you. Might be missing a few of the tables I defined in my EFI file, but I think it's about 80-90 percent complete and has enough table definitions to get the job done. Shoot me a PM and I can send it over.
Cruising
Joined: May 2018
Posts: 12
Likes: 7
From: SoCal
On a good note, I was able to open the XDF files both with Tuner Pro and HP Tuners ... I see new parameters. 
________________________________________ ________________________________________ _________________
Questions:
Thank you good Sir.
________________________________________ ________________________________________ _________________
Questions:
- As I looked over the files that you PM'd me and I am curious as to what the CTZ/CAX files are?
- Just to verify, are the (2) XDF files the only ones needed for getting the Flex Fuel working?
Thank you good Sir.
Cruising
Joined: May 2018
Posts: 12
Likes: 7
From: SoCal
Houston we have success!
Aaron, the two XDF files you provided and [blackvette82] C5 E85 Tune file for settings together got this all working.
I have a few images showing the XDF files loaded in HP Tuners along with a data log showing alcohol percentage registering with the help of Jack Daniels
Proof.
Aaron, I will email the images to you since it does not look like I can upload on the site, yet.
Cheers
Aaron, the two XDF files you provided and [blackvette82] C5 E85 Tune file for settings together got this all working.
I have a few images showing the XDF files loaded in HP Tuners along with a data log showing alcohol percentage registering with the help of Jack Daniels
Proof.
Aaron, I will email the images to you since it does not look like I can upload on the site, yet.
Cheers
Instructor
Joined: Feb 2006
Posts: 231
Likes: 11
From: Cleveland Georiga
Has anyone seen this? Or tried this?
https://www.thetuninglab.com/product...r-99-02-f-body
The Tuning Lab is proud to release a PnP flex fuel solution for 98-02 F-body/00-04 C5 corvette vehicles. Use these kits to add the ability to run anywhere from straight gasoline to straight ethanol as well as reveal the true power potential of your setup. Forced induction applications benefit from the use of ethanol, and this kit allows you to switch between gasoline and ethanol without having to monitor your fuel content or adjust your fuel tables. This kit is 100% Plug And Play. Picture is for display purposes ONLY.
NOTE: Due to the nature of the 0411 (the PCM that comes factory with the F-body) flex fuel logic is limited to 2 bar (up to 14 psi of boost). If you plan on running more boost than that, please purchase a P59 PCM as it will allow you to run up to 30 psi of boost.
https://www.thetuninglab.com/product...r-99-02-f-body
The Tuning Lab is proud to release a PnP flex fuel solution for 98-02 F-body/00-04 C5 corvette vehicles. Use these kits to add the ability to run anywhere from straight gasoline to straight ethanol as well as reveal the true power potential of your setup. Forced induction applications benefit from the use of ethanol, and this kit allows you to switch between gasoline and ethanol without having to monitor your fuel content or adjust your fuel tables. This kit is 100% Plug And Play. Picture is for display purposes ONLY.
NOTE: Due to the nature of the 0411 (the PCM that comes factory with the F-body) flex fuel logic is limited to 2 bar (up to 14 psi of boost). If you plan on running more boost than that, please purchase a P59 PCM as it will allow you to run up to 30 psi of boost.
Last edited by mddrip; Dec 29, 2020 at 12:30 PM.
Melting Slicks
Joined: Oct 2000
Posts: 2,726
Likes: 24
From: Freehold, NJ
Has anyone seen this? Or tried this?
https://www.thetuninglab.com/product-page/flex-fuel-kit-for-99-02-f-body
https://www.thetuninglab.com/product-page/flex-fuel-kit-for-99-02-f-body
https://www.thetuninglab.com/product...r-99-02-f-body
Instructor
Joined: Feb 2006
Posts: 231
Likes: 11
From: Cleveland Georiga
Melting Slicks
Joined: Jun 2005
Posts: 3,088
Likes: 61
From: NY- 2013 Corvette Challenge Champion-2013 Index Combo Champion 2015 CC/MM Champion
St. Jude Donor '07
Melting Slicks
Joined: Oct 2000
Posts: 2,726
Likes: 24
From: Freehold, NJ
Melting Slicks
Joined: Nov 2013
Posts: 2,049
Likes: 316
From: USA
Not a whole lot of info on the product site..... does it include a tune of sorts included in the price? Or just the hardware?
For Corvettes and if you want to retain all functionality, P59 is the way to go
For Corvettes and if you want to retain all functionality, P59 is the way to go
