Open Flash Flex Fuel Issues
 

Hey Everyone, I've searched and searched but haven't found a similar issue to what I'm facing. About a year and a half ago I set up an Open Flash flex fuel kit in my brz and purchased a custom OFT FF tune. It's been great up until the other day.


I was driving and my car started accelerating roughly anytime I got on the throttle over maybe 10-15%. I drove home nicely and plugged in the OFT to see if I could see anything. Turns out Ethanol percentage was showing at 11-12% (I had E70 in the car) and the fuel trims were insanely high (+40%). I then uploaded the e85 only OFT tune and just as expected, the fuel trims were perfect. This leads me to believe something is going on with the FF kit. It's not interpreting the correct E% and as a result, incorrectly adjusting the fuel.


I went over the connections and everything looked solid. Fuses were intact, ground was grounded and the signal wire was still connected to the ecu. I've emailed open flash and waiting on a response but curious if anyone here has any ideas of what could be going on? Also worth noting that I flashed back to the FF tune, and the E% with the same exact gas was showing 5.4 % now.. Seeing as the fuel trims are great and there are no knock events on the e85 tune, the gas isn't bad, right?

Sounds like the flex fuel sensor itself is not working, or is not getting a signal out. I would check the harness from the sensor out to see if it is chaffed anywhere. If not it may be a bad sensor.

You have a bad flex fuel sensor. Since you bypassed the FF sensor and car runs fine on e85 non FF tune. Happened to me before.

Looks like the sensor is actually fine. I got a new one and had the same issues. Turns out it’s the “converter” (not sure what it’s called but the black box in the middle of the wiring that converts the frequency to volts.. pretty much screwed since I can’t find the damn harness/box anywhere to wire a new one in hah

Open circuit the evap flex input on ecu the oft should read about 85% ethanol, ground the evap input on ecu should read arroind 0% ethsnol


The flex output from kit at 70% ethwnol should be arround 3.5-4 v

Thanks. Looks like voltage is 0 but I’m getting the proper frequency reading from the sensor itself so my best guess is the ethanol content analyzer went bad? I was able to buy a new oft harness from someone on here who had one they aren’t using anymore thankfully. Hopefully not a common issue with these kits and the new harness ends up working.

If anything, you can probably make your own converter using arduino. There are tutorials/codes online to help convert the HZ from the ff sensor to voltages (iirc OFT FF tune is 0.5-4.5v). Other option is that you can get the off the shelves ECA (zeitronix is one example) and have Steve99 create you a new tune to run 0-5v instead.

Thanks for the idea, found a post by ztan for how to do it so just going to build one. Tried finding someone with a kit they want to part out but they all ended up being scammers.. building one is way cheaper so can just keep building them if they continue to break, seems like the best way. Thanks again!