P59 COS3 04073003 flex fuel issues

So i did some searching here and on hptuners and sloppywiki. I am trying to get my content sensor up and going. First i flashed a custom os 040730003 in then flashed a 04 tahoe with flex enabled cal. Read it out. Did segment swaps from the old os that had flex turned off. Full flashed that in. Pin A is flex input pin 59 blue connector Pin B is ground. Pin C is 12v switched power. The sensor is a continential style from ecumaster.com came with a nice 6ft pigtail. Turn the key on and percentage is stuck at 0% i have a 26 gallon tank has 22gal of 91 and 4gal of e85 just to test. Figured id start with a small amount of e85 just in case near as i can tell assuming im getting E70 (.70x4=2.8gallons of pure ethanol) so (2.8/26=10.7%) so i should be seeing at least 10% on the scanner correct? Any help would be great!

Should be Blue Pin 56 no? Also post tune file

sorry yes it is on pin 56

this file is current

Flex fuel isn't fully enabled in the tune, probably got dorked up when you did the segment swap back to old OS that it wasn't enabled on. Best thing you can do is install a cax that maps those hidden FF tables so you actually know what's going on with the calibration.

See link below. Rename one of the cax files to 040730003.cax and compare to one of those corvette files or 04 tahoe file that is -7603 OS and check out all the FF related tables to make sure you have sane values. I saw a bunch of the tables in the "flex fuel" folder need values and don't forget about the spark blend table(s) as well. There's also quite a few cranking fuel tables.

Another random note, right after a flash I think it's pretty normal for ethanol content to read 0, until you start it up and then the value will slowly creep up to actual ethanol content. For example just today, I flashed my car, started it up...content was 0, and then crept up to 12.2 percent in about 30 seconds to a minute.

https://forum.efilive.com/showthread...Corvette-Files

Okay i will try that. I ran the car for quite a while and content never increased.

please forgive my ignorance but i have no idea how to create or make a .cax file thought i did but.... i guess not tried looking on the forum with not much luck seems as tho everyone that asks is one step ahead.

Drop the cax file in C:\Program Files (x86)\EFILive\V7.5\Calibrations

Then compare to the Tahoe FF enabled tune file to see what FF settings needs adjusted and a good starting value etc.

See attached zip below

thank you so much ill see if i can fumble thru this!

im sorry ive never done this before so i dropped the .cax in the file you stated now how do i compare to the stock tahoe file? which program? like i said i am sorry for being ignorant but ive just never had to mess with this stuff before im trying to learn. like ive never messed with any of this before today. all ive ever done is what the base efilive software allows.

The cax file is basically defining several more tables that are present in the PCM, but were not ever defined by EFI Live back in the day when they worked on it.

You'll find most of the new tables under Fuel->Flex Fuel, but also a few in Spark->General and Fuel->crank/start

okay so basically i put that file in C:\Program Files (x86)\EFILive\V7.5\Calibrations then open my tune as normal and compare to the tahoe ff? is that correct?

Correct

Attachment 23439

so basically this .cax file allows you to compare dissimilar os's that are the same base?

No you've always been able to compare base OS against the COS versions of that OS. The cax just defined some more flex fuel tables, ones that you need to change to make flex fuel work. Open up the cax file in notepad and you can see what tables were added.

Huh well i learn something new everyday. I did look thru the cax file in notepad its kind of like adding a custom pid sort of i guess in a way i was just so completely lost. I really appriciate your time sir and i will do my best to share what ive learned. Thank you.

Nailed it man thank you so much!!!!!!

no problem, you can look at commanded AFR to make sure it's changing with ethanol content as well. If you want to add spark with ethanol there's a few tables for that in the spark section as well.

yeah my plan is to leave boost where it is and increase power with timing while checking plugs for the time being. ill log timing tomorrow and see what its doing to make sure im not to advanced

so if you will explain to me where that cax file comes from and hows its made? is it all just "you have to know how" to make it? is there somewhere i can learn to do it?

1.) in the same "calibration" folder there is a template.cax that spells out how to create the files, the syntax associated etc. I also just looked a examples posted on here.
2.) You have to know the memory address for the value or table you want to define...........how do you know that.... there's now quite a few open source tuning solutions out there and some of them have tables of interest and you can skim thru those config files to get what you need. Also you can take a raw binary tune file and use a disassembly program to find these....this is not trivial process.
3.) Once you have that info you still need to know the scaling for the values and table dimensions, how many bytes each value is etc.

So this maybe falls into "you have to know how" category but I was able to figure some of it out myself, but it was many hours of reading and experimentation etc. And I am no pro by any stretch of the imagination, just starting to scratch the surface of this stuff.

Thats awesome thank you for sharing man i really do appriciate it i dont qant to ever take credit for anyones elses work but i do want to be able to do it on my own. I just recently(within the last year) started tuning ls1b ls1a ect so its incredibly exciting for me. I realize im like 20yrs behind rhe times but i still am fascinated by the amount of control you have tuning the stock pcms.

Also there's no way i would have been able to do any of it without this forum and all the amazing and talented people on here like yourself. Many hrs spent on here before i ever hit a key on the computer.

There is good wealth of info here.