Flex Fuel reading 4v problem

N111cuk

Lurker
Aug 8, 2018
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Hello to anyone who can assist me with my Flex Fuel issue

I have setup flex fuel using a specific MHD tune from an experienced tuner (JSR) and a fuel-IT ethanol analyzer which can read over bluetooth plus on a 0-5v signal wire

My setup; The ECA analyzer wire plugged into Harness PIN#16 on the black 26 pin sub
Capture2.JPG

Issue I'm having is #pin16 has 4v coming out of it which is normal based on my testing this car and others. However when I plug my ECA signal wire which currently has 0.28v (pump gas) it doesn't change the PIN16 voltage to the ECA reading but rather keeps the 4v resulting in a E reading of E80 on MHD and my JB4
Capture3.JPG

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My fuel-IT app shows E4 which is correct based on pump gas and 0.28v which I measured with a multimeter

My tuner has double checked the tune and seeing as I can see E content in both MHD and JB4 it looks right. But because I have a persistent 4v on PIN16 my E content is skewed

Important to note;
I installed a new DME MSD81 which came from a 135 from 2008 from the USA. I have my old mds80 but is now not coded to my CAS

I have a theory which comes from looking at the wiring diagrams attached in the PDF at the end of my thread

In the USA PIN 16 and PIN17 were used for these functions

16 E USA Signal, fuel tank leak diagnosis pump Diagnostic module for fuel tank leakage
17 E USA Signal, fuel tank leak diagnosis heating Diagnostic module for fuel tank leakage

Could I have a coding issue on this DME which means a conflict between function ????

I did also try plugging in the ECA signal only into the JB4 PIN2 on the DB25 plug and E shows up correct. the analyzer is working as intended

All I can think is at fault is the DME coding is somehow causing the issue
 

Attachments

  • Capture4.JPG
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  • 2008 BMW 335i Wiring Diagram - DME.pdf
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langsbr

Captain
Apr 5, 2017
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07 335i 6MT e90
Your Motiv ECA is likely bad. This just happened to mine. ECA voltage stuck at 4.02V and 100% ethanol. 4V is an error voltage from the Motiv ECA.

It appears you have 2 ECAs - the Motiv one and the Fuel it. You could remove the Motive one and run just the fuel-It, but you'd have to have to scaling for ethanol changed in your tune.

Motiv was very responsive and took care of mine with no issue. Sent it back and got a new one, plugged it in and back in business.
 

N111cuk

Lurker
Aug 8, 2018
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Your Motiv ECA is likely bad. This just happened to mine. ECA voltage stuck at 4.02V and 100% ethanol. 4V is an error voltage from the Motiv ECA.

It appears you have 2 ECAs - the Motiv one and the Fuel it. You could remove the Motive one and run just the fuel-It, but you'd have to have to scaling for ethanol changed in your tune.

Motiv was very responsive and took care of mine with no issue. Sent it back and got a new one, plugged it in and back in business.
I only have the fuel-it analyser
When tested I get 0.28v from its signal wire.
This is in-line with its reading in the app of e4

Issue happening when I connect the signal wire to my harness pin16
This pin16 is outputting 4v and once connected should be overridden by the eca signal voltage

I've since plugged in another dme and I have the same results

I think it's time to try another eca analyser
 

langsbr

Captain
Apr 5, 2017
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Oh I see, very good. Most people try to use both, which never made sense to me. I think that is what Motiv recommended originally as well.

When you say that pin 16 is outputting 4v, do you mean from the car? It shouldn't matter as that wire gets removed and not used - if I recall, that is the DMTL pump, which I thought looked for 5V, if your car is non-USA I think that pin is not used. When I reverted my wiring back to stock while my ECA was being RMA'd, the ECA voltage always read 5V.

Did you already flash a flex fuel tune and have purchased the MHD flex fuel option? I believe that option is what has the logging look at the DMTL pin for ECA voltage. It would not make sense that the DME would read that as 4V if it definitely has only .28v going into it.
 

langsbr

Captain
Apr 5, 2017
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07 335i 6MT e90
I found this from Jake, one of the MHD devs - he created Flex fuel:
1642369785109.png


Not sure how your scenario works with the MSD81 fom a USA car though.

@[email protected], if he is running a Euro car with a USA DME, should flex fuel read correctly?
 

N111cuk

Lurker
Aug 8, 2018
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Thanks for throwing ideas about.

Pin16 was empty on my harness, I added a wire to this position for FF.

I measured three different dme's and all had 4v o that pin, so my guess this is normal.

I think my eca doesn't have enough current to effect the ecu pin 16 to change its voltage and hence translate it into a reading of ethanol
 

N111cuk

Lurker
Aug 8, 2018
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I found this from Jake, one of the MHD devs - he created Flex fuel:
View attachment 64010

Not sure how your scenario works with the MSD81 fom a USA car though.

@[email protected], if he is running a Euro car with a USA DME, should flex fuel read correctly?
I have tested 2 euro msd80 dme and my current dme was from the states msd81 sent to me by motiv. It came from a 135i

All of which had pin 16 active showing 4v.

I'll throw some ethanol in and see if the voltage of the eca changes and also check its power and ground wires.

Maybe the current on the signal wire is too low
 

langsbr

Captain
Apr 5, 2017
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It's odd that you're getting voltage at that pin rather than it being a pin that looks at voltage. Hopefully Jake can shed some light on it.

I wonder if the MHD flex fuel module changes the functionality of that pin. Did you already purchase that option in MHD?
 

[email protected]

Captain
Platinum Vendor
Nov 7, 2016
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Philly
4V is the "float" voltage of that pin, and is correct -> this is what it should read w/ nothing attached. If your ECA is not being read at that pin, I would multimeter the output of your ECA to verify it is sending a correct voltage.
 

N111cuk

Lurker
Aug 8, 2018
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4V is the "float" voltage of that pin, and is correct -> this is what it should read w/ nothing attached. If your ECA is not being read at that pin, I would multimeter the output of your ECA to verify it is sending a correct voltage.
My multimeter reading on the ECA wire was 0.28v which is E4 and my fuel-it app confirms e4
 

langsbr

Captain
Apr 5, 2017
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07 335i 6MT e90
I would presume the MHD "flex fuel license" is a required purchase to run a flex fuel tune, but I could be wrong. If not, I feel like a sucker for paying for it if my tuner could just flash a flex fuel map. If it is required, have you purchased the flex fuel license?
 

[email protected]

Captain
Platinum Vendor
Nov 7, 2016
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Philly
Flash was made by JSR who double checked the tune. In mhd I read e80 and eca voltage as 4v. I've ordered a new adapter from fuel-it to see if this could be the issue
Try applying a different voltage to that pin with another source (in the 0-5v range), and see if the corresponding DME ECA Voltage param reads it correctly).

I would presume the MHD "flex fuel license" is a required purchase to run a flex fuel tune, but I could be wrong. If not, I feel like a sucker for paying for it if my tuner could just flash a flex fuel map. If it is required, have you purchased the flex fuel license?
Yes the FF license is required whether you flash a custom tune or OTS tune