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I'm writing this to try and help some folks out. The information surrounding this seems vague at best and searching often results in threads that never answer the question, but turn into a whole other subject matter when folks start asking about engine setups.

This is about adding a Flex Fuel sensor to a 2004 GTO using the stock ECU that the car comes with. That's it.

Stuff you need:

1. A flex fuel sensor. There are a few to choose from. I used this: Delphi P/N 13577429 (genuine OEM Continental sensor) I bought it from here: https://www.racetronix.biz/product.asp?ic=13577429

2. You'll need at least one of those little bitty pins that go inside the harness. I found a place that sells them; EFI Connection in Erie, PA. The other option is run down to a junk yard and buy a segment of the harness going to the ECU for any 2004/2005 GM car/suv. Snip it off a few feet from the plug. Then you just get the pin out of the plug and pull the entire wire with pin attached. Either way, pretty easy to do and cheap.

3. Flex fuel sensors are stupid simple in how they function. All it does is look at the color of the fuel. Colorless means more ethanol. Darker means more gasoline. That's it. The sensors have 3 wires. White=signal that you run to your ECU. Red=switched 12v power. Black=chassis ground.

If you are electrical idiot guy (like me) switched 12V power just means that you wire this into something that only has power when the key is in the ignition and you've switched it to "on". Running this sensor to a non switched 12V source would work fine, but it will cause a drain on the battery.

4. On 2004 GTO's the ECU lives under the big coolant tank on the D Side. You'll have to remove that tank. If your a bad ass you can move it without slopping coolant everywhere. I am not a bad ass so I drained it first. That kinda sucks as getting the coolant system air free is a little work, but whatever. Once the tank is pulled you wrestle with the black plastic cover that acts like an umbrella on the ECU. Get that off and you see two plugs retained by a single 7mm hex head screw. Ok, you are now ready to remove one of those.

Important: STOP and DISCONNECT your battery cables from your battery. ONCE and ONLY AFTER you have REMOVED BOTH battery cables, touch the two cables together. Again. ONLY after you have removed them from the battery! The reason for this is to kill any static or residual current that might be lingering somewhere. It's probably not even needed, but I am a bit paranoid when working with anything ECU related. Just like a computer at home, static can make a mess of things.


Ok, remove the 7mm screw from the harness on the INBOARD side of the ECU. Once removed it will have a blue color on the plug. The plug has a funky plastic cover/shroud that is clipped on each end and in the middle. As with any wiring things, its kind of a PITA to remove. Patience works here. Just pinch and tug. It will come off. It will likely have a single zip tie holding it to the harness. You do not need to cut the zip tie.

5. Now build or get your wire. Give yourself 3 or so feet of total length. Inspect the back side of the plug. Those pins are numbered. #56 is the one you want for the 2004 GTO. Inspection will show it has a rubber thingy in the hole. Just poke it with a pick. It'll perforate and that'll allow you to shove your pin in. Carefully install the pin from the back side. You'll need to push fairly hard to get it fully seated. You can hear a very faint click once it seats. Attempting to remove it by tugging the wire will confirm if you have it right or not.

That's it. Now reinstall the plug and put stuff back where it goes opposite of how you started. Leave the battery alone for now.

6. Run your wire to the white wire on the sensor. That is signal. The other two as previously covered are power/ground.

7. Plumb your fuel line to the sensor. I did mine on the return. I leave that decision to you. There's really no right/wrong answer here from what I can tell.

8. Now, using this thing:

The 2004 computer will support this upgrade. What will NOT work is the operating system currently installed in your car. For the illiterates this basically means that if you like using Cortana in Windows to look for stuff, you had to change the windows operating system to something like 10 or newer for you to use it in your PC right? The old days of using Window's XP just has no way of supporting it.

It's the same thing here sorta. We have to find a vehicle with an operating system that already has flex fuel capability and is also compliant with the ECU found in the 2004 GTO. This is pretty easy. The HP Tuner website has an archive called the repository. The "Hall of Records" for all things holy and related to this stuff.

What your looking for is an OS for a 2004 GM Fleet Van or an Escalade. There is no advantage of one over the other.

This OS gets loaded into your car via HP Tuner Sofware. If using EFI Live with a custom OS you'll need to just set it up that way.

Then its basically a function of ensuring the parameters in the software turn everything on and your tables for fuel delivery and igntion timing are calibrated appropriately. Be it either you or a well vetted shop doing that work.

But that is basically it and put into layman terms. I know I loath researching stuff where everyone talks in 3 and 4 letter codes that I then have to look up and decipher. Hopefully this helps. If there is something I left out, add to it but PLEASE SPEAK PLAINLY.

The whole point of a forum is to provide a platform for sharing information, not showing how smart you are with vocabulary abbreviations.

EDIT:

Here is a thread related to the fittings the sensors use: https://www.ls1gto.com/forums/showthread.php?t=835522


Hope this helps.

C.
 

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Awesome, simple, write up. If and when I eventually add flex fuel, I'll refer back to this.
 

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How different is adding flex fuel to a 05-06? I wouldn't mind running E85 but no one around me sells it
 

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Bad ass post LongRifles, I really appreciate the detailed write up. I am mostly clueless when it comes to electronics but I could do this with your post. Thanks for posting!
 

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Where did you dream up the info on the sensor reading the "color" of the fuel?
the sensors look at conductivity mainly. Add about a tablespoon of water in a quart of gas, keep it agitated and run it thru the sensor. it will suddenly show between 30 and 50% ethanol. and there was no color change...
 

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Thanks for the fantastic write up!

I have got the E85 sensor plumbed into my new fuel system but haven't wired it up yet or found an OS I am willing to try.

The problem I ran into doing my research was that the other vehicles OS's wouldn't work correctly with the GTO's, causing issues with the DIC and other glitches, esp for manual transmission GTO's. Did you have any related issues? How about OS segment swapping? Start with a) GTO OS, segment swap what you need from the Flex Fuel OS, or b) start with the flex OS and segment swap GTO segments back?

Edit - I think you want the Flex Fuel Tahoe (P59 PCM) not the Escalade. There is no 2004 Escalade Flex Fuel OS on the repository, but there is a Tahoe one for the P59.
 

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You can have a tuner turn the flex fuel on I. The stock ECU without flashing another vehicles Cal. The tables are there, they are all just zeroed out and flex fuel is disabled. The tuner can enable it and populate the tables

Sent from my SM-N950U using Tapatalk
 

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Discussion Starter #8
Where did you dream up the info on the sensor reading the "color" of the fuel?
the sensors look at conductivity mainly. Add about a tablespoon of water in a quart of gas, keep it agitated and run it thru the sensor. it will suddenly show between 30 and 50% ethanol. and there was no color change...

The department manager of Lingenfelter Performance's engine calibration; Brent Malone. That is where the information came from. He is who is helping me with my setup.
 

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Discussion Starter #9
You can have a tuner turn the flex fuel on I. The stock ECU without flashing another vehicles Cal. The tables are there, they are all just zeroed out and flex fuel is disabled. The tuner can enable it and populate the tables

Sent from my SM-N950U using Tapatalk

For the 2005's and 06's yes. On OEM 2004's those tables don't exist. Least they didn't on my car.
 

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Discussion Starter #10
Thanks for the fantastic write up!

I have got the E85 sensor plumbed into my new fuel system but haven't wired it up yet or found an OS I am willing to try.

The problem I ran into doing my research was that the other vehicles OS's wouldn't work correctly with the GTO's, causing issues with the DIC and other glitches, esp for manual transmission GTO's. Did you have any related issues? How about OS segment swapping? Start with a) GTO OS, segment swap what you need from the Flex Fuel OS, or b) start with the flex OS and segment swap GTO segments back?

Edit - I think you want the Flex Fuel Tahoe (P59 PCM) not the Escalade. There is no 2004 Escalade Flex Fuel OS on the repository, but there is a Tahoe one for the P59.


With my setup its no longer an issue. I went to a full manual valve body 4L80. Reverse pattern, trans brake, etc... The only wires touching it are the brake and the speedo sensor.

Tahoe/Escalade. You may very well be correct. A number of folks told me Escalade. I went with a plain jane fleet van the first time around, but never actually had the FF sensor wired up. I was still running through the pump fuel tune.

For me, now this is sorta mute. I made the jump to EFI Live about a month or so ago. I just like it better. After talking with Robby (engine builder) were going to go straight E85 from here out. I more or less did this just to hopefully have it as a sort of buffer should I ever be in a pinch and have to put "soft" fuel in it

With the custom OS platforms they have it does a whole lot of things that I struggled with in HP Tuners. We'll see soon enough. I am hopefully picking up my engine from McCabe Motorsports sometime next week.
 

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The department manager of Lingenfelter Performance's engine calibration; Brent Malone. That is where the information came from. He is who is helping me with my setup.
Wow,
If that came from anybody working on my car, I'd pack my crap up and go elsewhere.
There are plenty of demos, tests and descriptions on the flex fuel sensors and how they work, and not one goes by "color". they are all based on chemical properties. If they were based on color, as the sensor aged, it would tell the ECU that it was 0% alcohol. Gasoline darkens the insides of the lines with deposits from it's additives etc.
If you ever look at the inside of a fuel line, metal fuel rail etc that has been used more than about 6 months, you will see it starts as a tan, and slowly changes to a light brownish/orange. even with the best fuels. Carb cleaners etc don't remove the coloration either.
 

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For the 2005's and 06's yes. On OEM 2004's those tables don't exist. Least they didn't on my car.
Ah,
Assumed they were similar, even though they are a different ECU.
 

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Wow,
If that came from anybody working on my car, I'd pack my crap up and go elsewhere.
There are plenty of demos, tests and descriptions on the flex fuel sensors and how they work, and not one goes by "color". they are all based on chemical properties. If they were based on color, as the sensor aged, it would tell the ECU that it was 0% alcohol. Gasoline darkens the insides of the lines with deposits from it's additives etc.
If you ever look at the inside of a fuel line, metal fuel rail etc that has been used more than about 6 months, you will see it starts as a tan, and slowly changes to a light brownish/orange. even with the best fuels. Carb cleaners etc don't remove the coloration either.

You are in fact correct on the sensor. I should have been a bit more thorough. I just asked him about it and he admitted it was info he was given by a 3rd party. He's just "used it". I guess how it works isn't nearly as important as ensuring that it is working.

As far as qualifications go, I trust him. He's done some very good work on my vehicle via remote tune and he's been personally interested in getting it right from the start. My car is fairly unique and the driveability/power output is pretty stout.

Here is my build: https://www.ls1gto.com/forums/showthread.php?t=832905

Live and learn.

Links:

https://cecas.clemson.edu/cvel/auto/sensors/flex-fuel-sensor.html

http://nootropicdesign.com/projectlab/downloads/mq-3.pdf
 

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VERY nice!!

Sent from my SM-N950U using Tapatalk
 

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So you never mentioned exactly what you did for tune. You downloaded a file for a van or Escalade and loaded it to your ecm? How? Did you do a full write? I always thought it would not let you load a calibration from another different vehicle ecm.
 

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So you never mentioned exactly what you did for tune. You downloaded a file for a van or Escalade and loaded it to your ecm? How? Did you do a full write? I always thought it would not let you load a calibration from another different vehicle ecm.


Here is where I'm at in this so far:

There's a guy from Indiana, Brent Malone. Brent owns "Mal Cal". He's been helping me thus far with the software side of stuff. The first time around on pump gas I was using HP Tuners. I got it to idle, drive, etc on gasoline. the sensor was plumbed, but not wired.

Engine has been out of the car the last month. I pick it back up later this coming week. I'd made a goof (my fault) and hurt it.

As it stands right now. We have a 3 bar "custom" OS installed from EFI Live. I bought that software as well. (FWIW, I like that setup much more than HPT as it just formats in a way that I understand better)

So, we loaded that OS and then took a stock GTO OS and did a partial write to fill in some blanks. From there its been worked on. Tables for fuel, timing, etc... have been updated.

One thing were debating on is changing it again. The GTO setup doesn't allow you to change the stoich value past 10:1. Stoich for E85 is 9.7 You can force it, but the background calculations can get goofy.

The plan moving forward is to look for a manual trans, 3 bar OS that is E85 capable. My transmission is a full manual 4L80. Only wires to it are the speedo sensor and trans brake.

To answer your question more directly, you can load an OS from another vehicle. You just have to ensure it uses the same ECU. The ones folks seem to gravitate towards are the 04 fleet vans. They came FF ready. The issue I'm running into is the 3 bar thing and getting the stoich values I'm after.

Still lots to do, but we'll get there.
 

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One thing were debating on is changing it again. The GTO setup doesn't allow you to change the stoich value past 10:1. Stoich for E85 is 9.7 You can force it, but the background calculations can get goofy.
This is a trivial difference. For starters this will only effect trims by a few percent, even if the fuel buy is actually E85. Much of the time E85 isn't 85 but a bit less. You can just adjust the injector tables a bit to compensate if you want.

This is not something major enough to make a major course correction on.
 

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One thing were debating on is changing it again. The GTO setup doesn't allow you to change the stoich value past 10:1. Stoich for E85 is 9.7 You can force it, but the background calculations can get goofy.
I was never aware of this limitation.

IIRC, I currently run ~10:1 on my 04, though, since it's a happy medium between summer/winter blends of E85, and I have the table set to 9.85:1 on my 05. I do recall setting the stoic table on my 04 in the 9's and never recall having an issue, unless i just never noticed.
 

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This is a trivial difference. For starters this will only effect trims by a few percent, even if the fuel buy is actually E85. Much of the time E85 isn't 85 but a bit less. You can just adjust the injector tables a bit to compensate if you want.

This is not something major enough to make a major course correction on.
I have the equipment to test fuel. I don't fill the car at the pump but rather have drums of the stuff at home so that I can "binge buy" the good stuff. So far, this summer has been great here in W. S. Dakota. It's all been 85 or more. One station tested at 90% even.
 

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I was never aware of this limitation.

IIRC, I currently run ~10:1 on my 04, though, since it's a happy medium between summer/winter blends of E85, and I have the table set to 9.85:1 on my 05. I do recall setting the stoic table on my 04 in the 9's and never recall having an issue, unless i just never noticed.

It's a soft limit. You can force it. As I'm understanding it, the 3 bar map plays into this some how. Tuning/calibration is something I am still learning and I freely admit I have a long way to go. Brent is who I defer to for guidance here.
 
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