Need help with my flex fuel conversion (2002 tahoe flex os in 2000 silverado)

[turdbow fteenthousand]

My truck- 2000 4.8
downloaded os- 2002 tahoe flex 12216125

Hi everyone. I wired up my gm flex fuel sensor today and downloaded the 2002 Tahoe flex fuel os. I wrote the Tahoe flex os to my computer and went in and changed all the parameters to match mine. I disabled VATS and got it to fire, and it does fire and run for a few seconds, but it goes dead lean and then dies. I can't run a log right now because the battery is dead from me trying to start it over and over, but I'll post my tunes. I can't figure out why it will fire and run for a few seconds then lean out until it's dead. Originally I thought it was the vats messing with the fuel pump but it runs longer than a couple seconds and I can hear the fuel pump running, plus it's disabled. I'm just missing something and I don't know what. Truck ran great when I rewrote my old tune back to it, then immediately rewrote the Tahoe flex tune and it leans out until it dies. Parameters are identical on both tunes. I don't get it.

park to drive enrichment, zeroed maf, stall saver, fans turned vats off.hpt

tahoe flex sd.hpt

[MikeOD]

You have the MAF table zero'd out, and the MAF codes set to no error reported. So it's leaning out because it thinks it should. You have to uncheck the boxes for the MAF codes, and then set them to MIL on first error. You already have the MAF fail high frequency set to 0, so once you make the change to the codes, it'll run.

That said, with the MAF table set to 0's, it's going to struggle to run when it hasn't yet set the MAF code, once the code sets it'll be fine. To get around that, after you dial in the VE, look at how much airflow the computer is calculating at idle and put that in the MAF table. It'll help with restarts after clearing codes without the MAF present.

For what it's worth, I've seen a few 2000 OS's where you could run the codes the way you have them, and be in speed density as a result still, with no code present, but on the 2002 OS's you have to have the code in the background. By unchecking the SES enable box, you won't have a light on your dash, but a scan tool will still pick up the code.

[turdbow fteenthousand]

Well I?m running the SD os on both, so I didn?t think the maf would still act funny like you said, And you?re right! My 2000 is runs great just the way it is, and I tuned my VE table for my cam and it runs great. The piece of info I guess I was missing was that the 2002 os won?t run without the maf fail codes like my 2000 os will. Thank you for your help!

[IARLLC]

Did you put your injector data into the Flex tune? The Flex injectors are a lot bigger, 33lbs if I remember correctly. Flex data without Flex injectors would cause a very lean rig.

[turdbow fteenthousand]

Just to be clear in case someone stumbles across this thread: Nothing mechanically changed on the truck except for the flex sensor. It's the same motor, injectors, cam, fuel lines and tuning parameters. The VE didn't change, the spark didn't change, the idle didn't change. I literally copied and pasted every single table over from the old tune to the new tune. The ONLY difference is that I wired in a flex fuel sensor, then wrote the 2002 Tahoe tune with all the copied tables over to my pcm.

It was definitely the MAF codes. It fired right up and runs pretty great. Since apparently the gasoline in my tank was E15 that changed my commanded AFR a bit and I guess I'll have to re-tune just a tad, but overall it worked.

I am having three weird issues now, however.

1- my "Check engine level" light on the dash lights up. It doesn't when I have the old tune in there, I double checked. As in: Tahoe tune, check oil level message is on, switch back to old tune, light goes off and stays off.

2- "Low battery" message is on. again, same thing, Tahoe tune the battery message appears and stays on, write the old tune back in, battery light goes off and stays off.

I'm guessing these first two are because the truck thinks it is a Tahoe. maybe I need a Tahoe alternator and oil level sensor or something. I looked all over the tune and couldn't find anything for those two parameters, so that's a bummer but at least it runs.

The third and most important is that the trans seems like it's dragging. I had this problem before with my old tune and messing with the MAF SES codes fixed it, but that fix won't work now because if I "fix" the trans issues by disabling the MAF codes (which works in the 2000 tune) then it wont run with the Tahoe tune.

TL;DR- just an update: engine runs good now. two warning messages that are somehow tune related, and trans seems funny now. Not sure how to fix it but at least anyone trying to put a flex sensor in 99-02 non-flex truck will know what to do if this happens to them. Heres the tune and log

tahoe flex sd.hpt

tahoe flex run.hpl

[turdbow fteenthousand]

update- engine runs well and alcohol sensor is working great. Trans feels fine now too.

I figured out in the system options table that the Tahoe has two "Alt Term" boxes checked and my old file only had one. I changed that to match mine exactly and I'm still having the weird battery warning light issue.

I never thought a battery warning light could somehow be related to a pcm file. It's really weird. I can load the new tune, get the battery warning light while I drive around, then load the old tune, battery light goes off and stays off until I load the new tune in again. Has anyone else ever experienced this before?

tahoe flex working maf.hpt

park to drive enrichment, zeroed maf, stall saver, fans turned vats off.hpt

As far as I can tell everything is identical. I can't figure out why on earth my truck only think it has a bad battery when the Tahoe tune is in it, and not when the Silverado tune is in it.