My current fuel trims - idle, 2000rpm, 3000rpm all no load

[2006Tahoe2WD]

This adds to the thinking that the base map doesn't not assume there is any ethanol in the gas. Therefore, when 10% ethanol is encountered the O2 sensors tell the ECU to run rich and the injectors get more on time. No real harm done, just some LTFTs that run a bit high.

This brings up the question - What is the protocol for the 2006 Flex Fuel Tahoes/Suburban/Silverado? Do they have the same connector?

 

[2006Tahoe2WD]

After more digging the PID hex is 52 (dec 82) for Ethanol Fuel %.
Still not sure if that can be pulled via the OBD port on my car.
I contacted OBD Link MX+ people and they responded that if I don't see it under the SAE PID list then it is not available on my Tahoe.

 

[2006Tahoe2WD]

Right, I have a couple that I've tried.

I attempted to connect the OBDLInk app on my phone to the MX+ dongle last night but couldn't get the mandatory firmware update (only able to do that with the OBDLink app) to go. I did it this morning in my daily driver, so now I should be able to try the custom PID using either the tablet or the phone.

Torque Pro didn't care that the MX+ firmware wasn't the latest.

I'm very interested if you are seeing or are able to pull up the PID for ethanol percentage. I would guess since you are flex fuel that PID should be available. All my attempts to get an ethanol percentage have failed. I think we both have the J1850 VPW protocol, which is the "old" slow type.

 

[Mudsport96]

@2006Tahoe2WD , do you know what operating system your tahoe ecm is running?
I have looked at os 9623, 7811, and 5114 all 2006 OS calibrations show a base of 38.007 percent of ethanol in the flex fuel section. All vehicles seem to have the tuning there in the ecm, but whether or not it was active from the factory is dependent on the specific vehicle. There is no alcohol composition checker outside of the flex fuel settings that I can find. So I am going to say that unless the flex option is activated you can't see it.

I will post a couple pics of the parameter location and hex info.

 

[2006Tahoe2WD]

@2006Tahoe2WD , do you know what operating system your tahoe ecm is running?
I have looked at os 9623, 7811, and 5114 all 2006 OS calibrations show a base of 38.007 percent of ethanol in the flex fuel section. All vehicles seem to have the tuning there in the ecm, but whether or not it was active from the factory is dependent on the specific vehicle. There is no alcohol composition checker outside of the flex fuel settings that I can find. So I am going to say that unless the flex option is activated you can't see it.

I will post a couple pics of the parameter location and hex info.

View attachment 426516View attachment 426517

Thanks very much for this. I think you must be correct that different models (e.g. flex vs non flex) have different PIDs that show up or respond.
Please stand by I'll check to see if my OBDLink software will show the OS name.
Yesterday I went to the 76 Station that is supposed to have non-ethanol fuel to see if the pump was labeled in some way. I also asked the attendant, he said zero ethanol but I don't have the feeling he really knew. I'm working my way toward an empty tank and then will fill up and see if the LTFTs change.

 

[Mudsport96]

I use obdlink mx+ to scan vehicles and I don't recall if it shows operating system or not. I get that info from either PCMhammer or LSDroid programs. But like posted, I don't know if it really matters. I think there was one other EARLY operating system that came before the ones I posted, but not sure how common it was. I think it was phased out pretty quickly and TSBs were issued to flash the newer calibrations. Even my tahoe that had the later 5114 system had a TSB to update to the final 9623 program. And that was done in 2021. What does the door sticker say was the month/year yours was built?

 

[2006Tahoe2WD]

In upper right corner "08/05". I guess that's the mfg date.
I could not pull up an OS name using MX+ and OBDLink. It might be there but I couldn't find it.

 

[Mudsport96]

Mine is also 08/05. So I would think yours would have had the 5114 operating system mine originally had. But with the flex not enabled.

 

[2006Tahoe2WD]

Mine is also 08/05. So I would think yours would have had the 5114 operating system mine originally had. But with the flex not enabled.

I have an idea to potentially relate LTFTs to EVAP flow. I added the commanded purge value to my "dashboard" on my MX+. Haven't tried it yet. I'm low on gas now and will soon buy the 100 octane 76 gas in hopes it is non-ethanol. Could be about $6/gal.

 

[2006Tahoe2WD]

An additional thought.... You read on the internet that the STFT and LTFT are added to get the actual trim that will be applied. Yes and no. My STFTs bounce up and down rapidly about +/- 2% -> +/-3%. Let's call it a 6% swing. I don't think the ecu would swing the fuel delivery 6% every second or so. Doesn't make sense. Probably the STFT values are gathered over ? 50 readings and an average is determined then some part of that average is used to adjust the LTFT.