E38 DVT fuel composition reset

[Gregs]

Just want to verify that i'm reading this correct, we should only click reset if the ethanol percent is less than 10% but greater than 0%. Here is a pic of the button in the DVT control panel.

23197

[GMPX]

Yeah I think that was correct (less than 10%), the sensor recalibrates to a non ethanol fuel.

[Gregs]

Yeah I think that was correct (less than 10%), the sensor recalibrates to a non ethanol fuel.

Thanks,

I see there is a toggle button in the tune to specify calculation vs physical sensor. Does anyone know if it's possible to convert to a real sensor and which pins on the PCM I would need to connect to?

[ScarabEpic22]

Yes, a pretty common thing to add an actual sensor as the "virtual" sensor kinda-sorta works. GM did it to try and remove the physical sensor cost, but I believe they added it back on later vehicles (don't quote me on this part). On the E38, the signal pin is pin 40 on the black X1 connector (there's a good writeup on g8nation as well). Make sure you change the sensor style to physical, and copy all the FF values over from a factory FF tune.

I'm in the midst of doing this on my Sonic (E78) so I can run E85 on it.

[Gregs]

Yes, a pretty common thing to add an actual sensor as the "virtual" sensor kinda-sorta works. GM did it to try and remove the physical sensor cost, but I believe they added it back on later vehicles (don't quote me on this part). On the E38, the signal pin is pin 40 on the black X1 connector (there's a good writeup on g8nation as well). Make sure you change the sensor style to physical, and copy all the FF values over from a factory FF tune.

I'm in the midst of doing this on my Sonic (E78) so I can run E85 on it.

Thanks for the info, i will checkout the writeup on g8nation. It's too cold to do a conversion in an unheated garage right now. I may end up disabling flex fuel until this spring when it warms up and I can do the conversion to an actual sensor.

A couple weeks ago I ran the tank nearly dry and filled up with E0 fuel. Reset the fuel composition. I noticed that the reset would set the fuel composition to 3.3% ethanol. As I've been driving around for the last while the number has slowly been trending upward. It's currently at 14% with E0 fuel! I'm going to start doing some poking around online to see if anyone understands the calculated formula that it's using. I suspect the computer's increasing fueling to bring the LTFT's into the 0 to -2 range.

[joecar]

The physical sensors are relatively cheap now, about $50 or so.