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Yamaha yec ecu temperature reading

Discussion in 'Tech' started by Shuma-gorath, Nov 22, 2018.

  1. Shuma-gorath

    Shuma-gorath Well-Known Member

    Hi, question about the yec temp readings in the software. How accurate is it? Just for curiosity i was looking at the monitors and it showed the temp 35 deg off what it should be. Has anybody else seen this or is it probably just a bad sensor. Thanks for the help
     
  2. lonewrench

    lonewrench Mr.Charles

    It’s been very very good for us always, don’t forget it’s in C not F.
     
  3. Shuma-gorath

    Shuma-gorath Well-Known Member

    K thanks, figured it was the sensor.
     
  4. Shuma-gorath

    Shuma-gorath Well-Known Member

    I was able to switch the sensor this weekend with a new one and am still getting wrong readings. Now its reading about 25deg off. Could the temp channel in the ecu be faulty?
    Side note, i have a aftermarket dash and use the dataloging plug from the yec harness and that temp output reads ok.
     
  5. RM Racing

    RM Racing Tool user

    You do realize the temperature display is in Celsius, right?
     
  6. Shuma-gorath

    Shuma-gorath Well-Known Member

    I do realize that. When the ambiant temp is 50f and the yec monitoring on the software is reading -15c i would think something is wrong
     
  7. RM Racing

    RM Racing Tool user

    Sounds like there might be an issue with the gauges. If the YEC (green) data signal is correct, that is from the ECU. As long as someone has not recalibrated that dash (which dash is it?), then the ECU has the correct resistance signal from the sensor.
     
  8. Shuma-gorath

    Shuma-gorath Well-Known Member

    The dash is a motec adl. I got the calibration from motec for the oem sensor. I wouldnt mind so much that it was off but it seams like the ecu thinks its still cold and fuels for cold motor. Idle doesnt drop all the way also. When the motor is at 190 the software is telling me it is at 130
     
  9. RM Racing

    RM Racing Tool user

    The sensor signal is a green/white wire. I would first check the resistance of that wire between the sensor and the ECU. If there is a bad connection or partially broken wire somewhere, you might see fairly high impedance. This might be feeding the ECU a false resistance for the sensor (BTW, 285-350 ohms at 80 degrees C). Other than that, it is a puzzling issue. Is this also a YEC harness?
     
  10. Shuma-gorath

    Shuma-gorath Well-Known Member

    Ill check the wire tonight and see what i get. Yes it is a yec harness.
     
  11. Shuma-gorath

    Shuma-gorath Well-Known Member

    I checked the resistance at the ecu plug. It was 4.12. Temp outside was around 40-45. Seems about right. So now it seams the ecu is not interpreting the signal correctly.
     
  12. MELK-MAN

    MELK-MAN The Dude abides...

    if you put the dash in 'diagnostic' mode, does the air temp sensor read the correct temp? you can also scroll through the diagnostic modes and read coolant temp. see what that says while in diag mode vs the temp reading at the dash.
    need a owners manual to interpret which diag reading corresponds to what data. (and will have instructions on how to put dash into diag mode)
     
  13. Shuma-gorath

    Shuma-gorath Well-Known Member

    I do not have an oem dash. I am reading the values from the yec software on the laptop
     
  14. RM Racing

    RM Racing Tool user

    This changes things a bit. It seems the problem might be with the software (IMHO). If the signal to your Motec dash is accurate, then the ECU is interpreting everything correctly, this is where that logger signal wire comes from. This is why the problem seemed so confusing. It's possible that there is some issue with the YEC software's interpretation of the signal rather than the ECU's calculation. It is pretty crude software. You might do some dyno testing to verify your fueling is correct, but I still think the ECU is receiving the proper temp signal.
     
  15. Shuma-gorath

    Shuma-gorath Well-Known Member

    Thats possible, but i definitely think the ecu is not reading it right and compensating for it. When i start it up at -20c the unburned gas is crazy. Also at 180f the ecu is reading 55c. The idle does not drop below 1600 even though i have it set at -1.
     
  16. RM Racing

    RM Racing Tool user

    Looks like the only step left is to replace the ECU. You could try adding a resistance (rheostat so you can change it) to the coolant signal to fool it, just to see what happens with your fueling.
     
  17. Shuma-gorath

    Shuma-gorath Well-Known Member

    I can try that but does the resistance increase as it heats up.
     
  18. RM Racing

    RM Racing Tool user

    That's what the rheostat would tell you. It's all relative, the rheostat is just a correction factor.
     
  19. Shuma-gorath

    Shuma-gorath Well-Known Member

    Ic thanks ill try it tonight.
     
  20. RM Racing

    RM Racing Tool user

    Tested one I have at the shop. Resistance at 20 c (average sort of room temp) is approximately 2600 ohms. Resistance goes down as it heats up. Double check the value into the ECU against ground.
     
    CUTBACK likes this.

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