Gen III Flex fuel Write-up
On The Tree
Joined: Jul 2007
Posts: 113
Likes: 0
From: Largo, Fl
This pretty much sums it up!
Make sure to grab a p59 from a cable throttle vehicle (van, 4.3, etc.)
Tach most likely needs a pull up resistor (Google it).
I've only had luck with flex fuel working on a factory flex fuel calibration. My go-to is a 2005 flex fuel avalanche. Do a write entire and change system options to function with cable throttle.
Make sure to grab a p59 from a cable throttle vehicle (van, 4.3, etc.)
Tach most likely needs a pull up resistor (Google it).
I've only had luck with flex fuel working on a factory flex fuel calibration. My go-to is a 2005 flex fuel avalanche. Do a write entire and change system options to function with cable throttle.
Ima post this here too.
I've done the Flex Fuel sensor install using OS 12216125. After locating a 4l80e file that uses the same OS and performing a segment swap the trans would not downshift from third to first when coming to a stop. Hptuners support sent me a different file which solved the downshift problem but now the TC will not stay locked in 4th and when the shift selector is in D3 the TC will lock even thou in the tune it should not lock in third at all. It will constantly lock then unlock until I let off the gas to get below my targeted lockup speed. Before the OS change the trans worked perfectly so I'm ruling out mechanical issues. Does anybody have a GOOD WORKING 4l80e file with the above OS that they don't mind sharing? Any suggestions relating to the problem is also welcomed.
I've done the Flex Fuel sensor install using OS 12216125. After locating a 4l80e file that uses the same OS and performing a segment swap the trans would not downshift from third to first when coming to a stop. Hptuners support sent me a different file which solved the downshift problem but now the TC will not stay locked in 4th and when the shift selector is in D3 the TC will lock even thou in the tune it should not lock in third at all. It will constantly lock then unlock until I let off the gas to get below my targeted lockup speed. Before the OS change the trans worked perfectly so I'm ruling out mechanical issues. Does anybody have a GOOD WORKING 4l80e file with the above OS that they don't mind sharing? Any suggestions relating to the problem is also welcomed.
On The Tree
Joined: Jul 2007
Posts: 113
Likes: 0
From: Largo, Fl
Ima post this here too.
I've done the Flex Fuel sensor install using OS 12216125. After locating a 4l80e file that uses the same OS and performing a segment swap the trans would not downshift from third to first when coming to a stop. Hptuners support sent me a different file which solved the downshift problem but now the TC will not stay locked in 4th and when the shift selector is in D3 the TC will lock even thou in the tune it should not lock in third at all. It will constantly lock then unlock until I let off the gas to get below my targeted lockup speed. Before the OS change the trans worked perfectly so I'm ruling out mechanical issues. Does anybody have a GOOD WORKING 4l80e file with the above OS that they don't mind sharing? Any suggestions relating to the problem is also welcomed.
I've done the Flex Fuel sensor install using OS 12216125. After locating a 4l80e file that uses the same OS and performing a segment swap the trans would not downshift from third to first when coming to a stop. Hptuners support sent me a different file which solved the downshift problem but now the TC will not stay locked in 4th and when the shift selector is in D3 the TC will lock even thou in the tune it should not lock in third at all. It will constantly lock then unlock until I let off the gas to get below my targeted lockup speed. Before the OS change the trans worked perfectly so I'm ruling out mechanical issues. Does anybody have a GOOD WORKING 4l80e file with the above OS that they don't mind sharing? Any suggestions relating to the problem is also welcomed.
Staging Lane
Joined: Jul 2006
Posts: 69
Likes: 0
Is there a way for me to check the voltage output of the flex fuel sensor to verify it is good? I wired it up, changed the tune and the car is running super rich and barely runs. The hp tuners scanner is not showing an ethenol content reading. Changed back to my prevvious tune and the car runs fine.
Pin 56 is going to the white wire. Pink is going to ignition voltage. Black with white stripe is going to ground.
Edit:
After looking at the original post it seems that going by just the colors the harness has pins b and c switched which is the power and ground. I will try swapping them in the morning and seeing what that does for me.
Pin 56 is going to the white wire. Pink is going to ignition voltage. Black with white stripe is going to ground.
Edit:
After looking at the original post it seems that going by just the colors the harness has pins b and c switched which is the power and ground. I will try swapping them in the morning and seeing what that does for me.
Last edited by jchevy; May 25, 2017 at 10:24 PM.
Is there a way for me to check the voltage output of the flex fuel sensor to verify it is good? I wired it up, changed the tune and the car is running super rich and barely runs. The hp tuners scanner is not showing an ethenol content reading. Changed back to my prevvious tune and the car runs fine.
Pin 56 is going to the white wire. Pink is going to ignition voltage. Black with white stripe is going to ground.
Edit:
After looking at the original post it seems that going by just the colors the harness has pins b and c switched which is the power and ground. I will try swapping them in the morning and seeing what that does for me.
Pin 56 is going to the white wire. Pink is going to ignition voltage. Black with white stripe is going to ground.
Edit:
After looking at the original post it seems that going by just the colors the harness has pins b and c switched which is the power and ground. I will try swapping them in the morning and seeing what that does for me.
You probably don't have a true flex fuel OS, if you did start with one in the beginning, you can lose flex fuel by doing some segment swaps. Pm me
Staging Lane
Joined: Jul 2006
Posts: 69
Likes: 0
Thanks for helping me out. I cant attach a tune in a PM so I will just post it here. I am using a p59 computer from a 2003 express. I have not upgraded to the newer express OS yet so all of the flex fuel tables are there except the open loop blend table. I havent done any segment swaps. Attached is the tune I am currently using. I am running speed density but not the custom OS speed density upgrade.
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Verdad Gallardo Thanks for helping me out. I cant attach a tune in a PM so I will just post it here. I am using a p59 computer from a 2003 express. I have not upgraded to the newer express OS yet so all of the flex fuel tables are there except the open loop blend table. I havent done any segment swaps. Attached is the tune I am currently using. I am running speed density but not the custom OS speed density upgrade.
Edit: alternativly I think you can get it working by segment swapping from a known good flex fuel file. The problem is that the OS must match.
Last edited by i420tom; May 26, 2017 at 08:54 AM.
Staging Lane
Joined: Jul 2006
Posts: 69
Likes: 0
Segment swap didnt help it still runs like crap...
Sensor is out putting 5.1 v...does this translate to 0% alchol content? What are the chances i have 100% gasoline in my tank? Im wondering if i could have fried my sensor messing around with the wiring.
Sensor is out putting 5.1 v...does this translate to 0% alchol content? What are the chances i have 100% gasoline in my tank? Im wondering if i could have fried my sensor messing around with the wiring.
On The Tree
Joined: Jul 2007
Posts: 113
Likes: 0
From: Largo, Fl
What trans are you running? Are you going boosted? Check the wiring on the sensor not the wiring diagram.
Staging Lane
Joined: Jul 2006
Posts: 69
Likes: 0
Let me try to wrap my head around whats going on. You are using a 03 express PCM, not running the enhanced speed density option, and you are trying to just enable the FF ? Am I missing something?
What trans are you running? Are you going boosted? Check the wiring on the sensor not the wiring diagram.
What trans are you running? Are you going boosted? Check the wiring on the sensor not the wiring diagram.
On The Tree
Joined: Jul 2007
Posts: 113
Likes: 0
From: Largo, Fl
Im used a P59 PCM with a Avalanche OS. Reason was I had a hard time finding one that had the 3bar enhancement and flex fuel using the P59. I would suggest doing the speed density enhancement, do a write entire and see what it does. Also, you may wanna try setting the MAF to fail as well. Also, you have to check It sounds like you are getting some of the flex fuel to work but the scaling is off. My car shows the alcohol content super accurately. I can add non-ethanol fuel and it registers almost perfect. Now, the sensor does have a small delay in adjusting for the actual % . After a fill up, it usually takes a min or two to change the value. I can give you one of my tunes, but it really wont run your car, but you can at least compare whats different.
This is a Bigmandengo special. 98 Trans Am, P59 PCM, Avalanche OS, 3bar, 4L60E, FF
Like I said before, Tylor is the man. Super nice guy, serving in our Military and loves boosted LSX stuff.
This is a Bigmandengo special. 98 Trans Am, P59 PCM, Avalanche OS, 3bar, 4L60E, FF
Like I said before, Tylor is the man. Super nice guy, serving in our Military and loves boosted LSX stuff.
On The Tree
Joined: Jul 2007
Posts: 113
Likes: 0
From: Largo, Fl
I managed to run my 2002 CETA with a 12216125 OS on the stock 411 PCM. But I'm having issues with the ABS light and fuel gauge. Would either of you guys running a 411 PCM with a 12216125 OS be willing to share your HPT file? I'd really appreciate it! 
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