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Looking for FFV info

8K views 23 replies 10 participants last post by  csoukup6 
#1 ·
Does anyone have any solid information on how the FFV system actually calculates the % of ethanol. Looking at different wiring diagrams the only difference that I can find between the flex and non flex fuel systems is the addition of a fuel pressure switching valve that is on the flex fuel engines. I can find no other different components between the FFV and non FFV systems. I wonder if Toyota even uses a dedicated sensor to monitor the alcohol content or if they calculate a value based on other variables like Ford does. Some of the Ford systems calculate the % of ethanol based on the O2 sensor readings. They do this by looking at the short term fuel trim readings after the vehicle has had fuel added. They figure that if after a fill up it takes X amount of fuel control correction to get the short term numbers to be where they want them to be that there must be a certain % of ethanol in the fuel. That is a very flawed way to calculate it being that any modifications done to the vehicle (intake, exhaust..etc) can mess with the fuel trim readings. Being that part of Toyota's reset procedure for the alcohol reading is adding at least 3 gallons of fuel to the tank I'm wondering if they don't use a similar method.

My reason for trying to figure this out is that I am looking for a 4x4 Tundra to replace my 2x4 Tundra and I am finding a shit ton of FFV in my area and I don't want to count them out just because of FFV issues. If I can understand how the system calculates alcohol % than there is possibly a way to trick it to think that the % is always the same.
 
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#2 ·
So after a little more digging I have a little more information. As I suspected, being that there is no actual sensor to measure the % of ethanol in the fuel, the % is inferred. At given times, the pcm will suspend various other operations and forget it's learned values so that it can look at short term fuel trim(stft) numbers (typically after refueling). Based on stft readings which are derived from the maf, ect and afr sensors, the pcm can determine what stoich is. As the percentage of ethanol goes up the engine needs more fuel to keep the stft numbers where it wants them, typically between -2 and +2. Now if the stft numbers start going higher than +2 the pcm assumes that the cause has been the addition of ethanol fuel, it thinks this because it monitors the fuel level sensor and saw an increase. The pcm starts correcting the amount of fuel it is adding to the engine until it can maintain the stft numbers in the -2 to +2 range. After it does this it calculates what the afr is and based on that it determines the % of ethanol. For 100% gasoline stoich afr is 14.5-15.0:1 but for e85 it is ~9.5-10.0:1, as the % of ethanol goes down the stoich afr follows it accordingly.

The big problem with this is that any modifications done to the vehicle that might alter the afr will throw this system for a loop because it is not figured into the programming of the pcm. Also any problem that the engine may be having that affects the afr but hasn't yet triggered a fault in the pcm will also throw this out of whack because the pcm suspends learned values while it does it's calculations so it could potentially think that the cause for the skewed stft numbers is due to ethanol being added.

I'm currently trying to dig up more info on exactly what conditions must be met for the pcm to run it's calculations...more to come.
 
#5 ·
Thank you for confirming what I've been seeing @l1tech when I look at the wiring diagrams.

If what we think is true (the %E is a calc value), then they really should be able to fix it with a reflash. I think that's why we've seen so many reflashes as the 'fix' while they try to identify the exact logarithm to use for consistent results. I just hope it's not a major logic re-write (propensity to introduce new quirks).

This was a terrible idea using calc values instead of just putting in a fukn %E sensor. I converted my FRS to run on E85 100% of the time with nothing more than simple ECM reprogramming. For less than 400 bucks I can put in a %E sensor and feed the %E to my ECM for an 'actual' value, allowing me to be flexfuel. I just never bother running on anything other than e85 in that car though. POWAAAH!! :)

If they want to go into the future with E85, they need to put an inline %E sensor to the fuel rail - that's the only solid solution.

My wife took our 2014 FFV in for it's first service today at 5k miles. She said they did some 'recall'. I'll update here if it was related to the FFV or even looks like it might be. We do switch between E and regular gas, and we monitor %E via DashCommand, but we live in AZ so it's never been cold enough to be an issue.
 
#6 ·
I had the recall done today. It is published as another AIP update for something to the effect of an iced or frozen valve. My service adviser claimed it also dealt with the FFV problems, but I haven't seen anything published to confirm this. You may not be cursed with the FFV problem on your vehicle.

Did you put a turbo kit on your FRS? Do you also have some sort of tune to run e85 (cheap race gas, in your case)?
 
#9 ·
I drove to Colorado last week and noticed before we got to the mountains mpgs started to suck and power seemed very lacking. I used my torque app and found ethanol readings of 76% and an afr of 9.6 while idling. My truck obviously thinks I'm running e85. When we arrived, most every morning, the truck had really rough starts. Temps are in the teens and 20s.

I figure one of three things happened, I got bad gas, the truck didn't like the way i fueled from 87 to 85 octane, or like mentioned above my tuner, bullydog trail tune, affected the afr enough to cause this. Or, maybe all of these things at once triggered it.

I tried pulling the battery cable for 45 minutes hoping it would reset the values, but it did not work. I'm going to uninstall the bullydog tuner and go back to stock to see if this will reset everything before I take it to the dealer.
@l1tech if you found anymore information on how it might be possible to trick the ecu into always thinking it's running regular fuel, I'd love to hear it. I'm not really happy with what happened and wonder if it's worth keeping a truck that does this. I love everything about my truck except for this. Also, it would be great to know of a way to reset this without having to reflash the ecu. Thanks!
 
#10 ·
Unfortunately there is no way to trick the ecm into a dedicated ethanol %. All bets on your truck actually having an issue are off until you remove the "tuner". Does the Bullydog trail tune make that much of a difference that you couldn't do without it?
 
#13 ·
I was thinking bad gas and cold weather triggered it. I monitored the ethanol each tank of gas on the way home and made sure to fuell and wait to drive off like the manual says. But it never went back to normal. I took the tuner off ( man, what a huge difference. My truck felt like it was so heavy. And even worse mpg on the way to the dealer) and drove to the dealer. They told me it was the programming and thier records showed that the last update i had, toyota determined that it didnt work. The advisor that helped me, let me know if it happens again, toyota athorized them to replace the fuel pump. Im good with that.
 
#18 · (Edited)
Does anyone know if you can get the loaded software version for the ECU using the OBD II tools ? I have a mod sticker that ends in 400 and the dealer told me the truck had the latest. I was at the dealer on 12/4/15, the sticker was on the truck when I bought it. Would be nice to verify whats really loaded. Version 600 could be loaded and the dealer just never put an updated sticker.

I'm using OBD Fusion.

 
#22 ·
I'm Using OBD Fusion for iPhone. Works pretty good. Need to dig around to see if I can see which software is loaded in the ECU.

My Alcohol % is reading zero but I learned from another thread somewhere on the forum that you need to connect you OBD and take the reading when you first refuel. Once the ECU reads ~14.99% or less it will set the Alcohol % to zero.

I'm going to try this tonight when I fuel up.
 
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