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Gen III Flex fuel Write-up

Old 07-03-2014, 01:44 AM
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Default Gen III Flex fuel Write-up

Ive already had alot of people asking me about this setup and a few wanting a write up so i will go into as best detail i can about this.

This will allow you to run any fuel and not worry about the ethanol content.

I did this flex fuel on my 1999 silverado. Basically the same as any 99-02 fbody. I did upgrade to the 0411 pcm which is common pcm for 99-02 camaros. The 99 truck pcms were known for problems which is why i switched.

I had already updated my injectors to 50 lbs flex fuel injectors. The part number for anyone wanting to use that is 12613412. They came off of 2010-2014 trucks with a 6.0. I am however still using the stock pump and havent had any problems.

Hardware-
1. You will need to tap into the fuel line somewhere. It doesn't matter whether it be the feed or return. Feed made more sense to me as the fuel will be analyzed before the motor sees it.
Since the sensor i was using had the same inlet and outlet size as my fuel line i used Russel fitting 644123, which is a 3/8 to stock fuel line fitting. I then used a -6 to -6 fitting then another fuel line fitting quick connect fitting.

Sidenote- For a fbody, The fittings may very but will generally be the same. there might even be more room on a camaro that what i had to work with.

2. Flex fuel sensor- As far as flex fuel sensors go, you have a few options.
13577429- This is the one used and is small and fits nicely. the price is nice also
13577394- Longer fuel leads but the same internally.
13577379- Same as above but has very short leads and i dont think the quick connect fittings would work.
Gm makes a very expensive one also, but dont waste your money as that one is the same as the ones above

3. Harness- I used 13352241 and hacked the end off i didnt need...

4. You will also need some wire and a pcm lead connector. I had a few from a pcm bench harness i made but if you don't have them the internet does and they are cheap. They are just Micro-Pack 100W 1.0 Terminals. Search that and find some!

5- HPtuners to Load the New OS onto your pcm.
12216125 - That is the os for the 02 Tahoe Flex Fuel operating system.

Wiring-
I am going to include the diagrams for the connectors and pcm to make it a little easier to see what im talking about. But the sensor just needs a ground, Which i ran to the nearest ground on my truck which was conveniently about 4 inches away but any ground will do.
Next is a switched power source, I looked on the diagram to see what the actual sensor is to be powered by. Pin 19 is an ignition power and is what the sensor should be powered by on the tahoe. Any switched 12v source will do if you cant find the 19 pin on the pcm. It was a pink wire on my truck.
The last on the flex fuel sensor is the actual wire which tells the pcm what content its seeing. This is pin 56 on the pcm.

Thats basically all you need to run a Flex fuel Pcm in a gen 3 vehicle. Now on to pictures of the install and diagrams.

Here is the sensor with my connector and the an fittings that attach to the fuel line.
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Pin 19 is seen here as ignition voltage.
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Here is the power for the sensor, You can see it runs off of the ignition voltage from pin 19.

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Flex fuel sensor connector view. As you can see its only 3 wires.

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Everything installed and wired. I ran out of wire wrap so it looks ugly now but im going to get more this week. And also dont mind the dirty and crazy injector harness.... But its in and runs amazing!
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Overall this was very worth it. Being able to run any fuel is very cool.
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Old 07-03-2014, 01:51 AM
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Nice job. I'm sure this information will help some people.
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Old 07-03-2014, 01:55 AM
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I hope so! it was hard to find info for it! hopefully this helps someone! My overall cost was like 100 bucks... sooo its really cheap depending on the fittings you choose!
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Old 03-02-2015, 09:13 AM
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Just read thru your thread...thanks a million for the information. This will make life so much more convenient. Any feedback on how the car has been running with the setup since the install?
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Old 03-03-2015, 01:17 AM
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This is cool.
I'd like to know if that OS is upgradeable to 3 bar?
If so, does the flex fuel still work?
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Old 04-18-2015, 07:55 PM
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Ok well this intrigued me so I decided to dive in and try this. I have the OS swapped to the 02 suburban flex fuel in my truck 411 type pcm , added the flex fuel sensor to pin 56 (early S10 aluminum style), and the tune changed with HP tuners. I am having some weird problems though, the alcohol content in the HP scanner is only showing whatever I set my default value to. It also doesn't appear to be changing the fuel trims to match the commanded afr. I am not getting any engine codes related to a faulty sensor so I am assuming its fine. Any advice would be appreciated. A working calibration file might be helpful to look at in case I am missing something. I have also attached mine if someone wants to take a look.
Attached Files
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BLAZER 5.3 FLEX FUEL.hpt (470.3 KB, 398 views)
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Old 04-20-2015, 06:16 AM
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Originally Posted by jonarotz View Post
Ok well this intrigued me so I decided to dive in and try this. I have the OS swapped to the 02 suburban flex fuel in my truck 411 type pcm , added the flex fuel sensor to pin 56 (early S10 aluminum style), and the tune changed with HP tuners. I am having some weird problems though, the alcohol content in the HP scanner is only showing whatever I set my default value to. It also doesn't appear to be changing the fuel trims to match the commanded afr. I am not getting any engine codes related to a faulty sensor so I am assuming its fine. Any advice would be appreciated. A working calibration file might be helpful to look at in case I am missing something. I have also attached mine if someone wants to take a look.
Disregard, I found my problem.
There is a lot of misinformation out there and I found some regarding the wiring of the sensor. The pinout I was referring to had pins A & C wrong. I swapped them around and everything works great.
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Old 04-20-2015, 10:54 AM
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If this can work with 3 bar I'm doing it
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Old 01-14-2016, 01:30 PM
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Originally Posted by SPRAYED 01 View Post
If this can work with 3 bar I'm doing it
Any follow up on 3-bar?
I have a 2002 lq4 drivetrain, which I could easily swap over the OS I think, but I need the 3-bar as I'm turbocharged.
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Old 01-15-2016, 03:11 PM
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Shouldn't have any problem using a 3 bar MAP when scaled correctly.
Still need both 93 tune on 3 bar and E85 on 3 bar.

Might want to see if Cobalt SS have flex fuel figured out, IIRC they come with 3 bar MAP.
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Old 01-16-2016, 04:25 AM
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Originally Posted by ryanleiker View Post
Any follow up on 3-bar?
I have a 2002 lq4 drivetrain, which I could easily swap over the OS I think, but I need the 3-bar as I'm turbocharged.
If you want 3 bar and flex fuel you must upgrade your PCM.
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Old 01-16-2016, 04:27 AM
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Originally Posted by imma_stocker View Post
Shouldn't have any problem using a 3 bar MAP when scaled correctly.
Still need both 93 tune on 3 bar and E85 on 3 bar.

Might want to see if Cobalt SS have flex fuel figured out, IIRC they come with 3 bar MAP.
Shhh don't speak of things you don't understand.
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Old 01-16-2016, 04:51 PM
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Originally Posted by eaglegoat View Post
If you want 3 bar and flex fuel you must upgrade your PCM.
Upgrade how?
Will the p59 pcm from a 2005 3500 6.0L express van work for this? I just got myself one of these.

Last edited by ryanleiker; 01-17-2016 at 11:37 AM.
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Old 01-22-2016, 04:26 PM
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From my understanding, the 05 express van pcm is the one to have, but if you have the older setup, you will need to move a few wires around in it to work. I am also in the exact same boat, and am trying to figure this out as well.

My current setup has the Blue/Red with a 01 truck OS. I will also be going to the 3bar OS from the 05 Express Van with Flex Fuel.
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Old 02-01-2016, 03:40 PM
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Blue pin 56 or red 56 pin?
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Old 02-01-2016, 11:30 PM
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Originally Posted by kaganader View Post
Blue pin 56 or red 56 pin?
I cant remember, its been a while lol
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Old 02-01-2016, 11:45 PM
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Originally Posted by ryanleiker View Post
Upgrade how?
Will the p59 pcm from a 2005 3500 6.0L express van work for this? I just got myself one of these.
Not positive about the 05. I use part #12586243.
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Old 02-02-2016, 09:55 AM
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Originally Posted by kaganader View Post
Blue pin 56 or red 56 pin?
Blue 56
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Old 02-03-2016, 12:55 PM
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Originally Posted by Agent_Orange_Shuvel View Post
Blue 56
Thank ya lol
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Old 02-03-2016, 01:07 PM
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Did anyone get this to work on a fbody? Does the bcm and stock cluster, abs still work when running the 05 van softwear?
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