TPS Sensor Questions

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by mdfehrmann, May 15, 2009.

  1. mdfehrmann

    mdfehrmann Been here awhile

    Joined:
    May 27, 2008
    Oddometer:
    338
    Location:
    Cleveland OhiO
    I searched for this and I'm sure the answer is here but I couldn't find it.
    What does the TPS actually do? Does it make adjustments to the timing based on the throttle position?
    I have a 06 950 if it makes a difference.

    Thanks dudes!
    #1
  2. StevenD

    StevenD Hmmmm, dirt!

    Joined:
    Aug 3, 2005
    Oddometer:
    1,277
    Location:
    Holland, Amserdammed
    deleted post due to uncertainty's still wheter it is actually used beyond emission stuff.
    #2
  3. Zuber

    Zuber Zoob

    Joined:
    Sep 28, 2004
    Oddometer:
    2,730
    Location:
    Main Street, Shedd, Oregon
    FOR 950 CARBS - the Throttle Position Sensor, TPS, sets the ignition advance. The ignition set the advance based on Engine RPM and Throttle Position. This is called a 3D Map, 1. RPM, 2. TPS, 3. Ign Advance.

    When you turn on the ignition, the small computer in the ignition looks for a 'referance voltage' to determine if the TPS is in range. The voltage should be 0.5-0.6 volts when the throttle is shut. You should always have the throttle shut when turning on the ignition.

    This referance voltage is set at the factory at engine idle. BUT, if the idle is turned down during the break-in period, then the referance voltage may be wrong! You may need to reset the TPS after the engine loosens up and the idle position is different. I've seen several 2006 950 Adventures with a too low voltage of 0.38 v. These had a bad surge around 3000 rpm. Reseting the TPS usually fixed it without re-jetting.

    If the ignition doesn't see this voltage during start up, it may not set the advance correctly and you'll get a surge between 2000-3800 rpm. This acts just like a lean carb condition. It can be masked by richening up the carb low speed mixture screws or low speed jets, but you'll get poor mileage and a weak low rpm throttle response. If the TPS is dirty or worn, you can get the same erattic behavior.

    The workshop manuals show how to set this. I'd recomend to try a resultant voltage very close to, but below 0.6 v. Check it several times by turning off the ignition and make sure you still have the same voltage when you turn it back on. Make sure it tracks voltage smoothly as you open/close the throttle. Any jumps, dead spots or other flaky action means you need a new TPS.

    I did a search for this subject and only found fuel injection subjects. If anyone knows of a thread, please add the link.

    <EDIT>(Edited on 2-20-11) .... Check this voltage between the Yellow and Black wire. Some early manuals have it different (blue/yellow) which is wrong. Just push the probes in past the rubber seals to touch the connectors. It is most critical to get the closing voltage between 0.5 and 0.6 v. <EDIT Out>
    #3
    chainbreaker likes this.
  4. AdvGa

    AdvGa Long timer

    Joined:
    Nov 25, 2009
    Oddometer:
    1,320
    Location:
    Atlanta Metro
    Zuber,

    Thanks for explaining the TPS in such great detail... I was wondering about this.

    I found my this wire connection had slipped off the Carb (due to loosening copper connector) last week and wondered just how much it affected the bike without EFI.

    Thanks again....
    #4
  5. Chuckracer

    Chuckracer Jerkus Maximus

    Joined:
    Aug 26, 2007
    Oddometer:
    9,241
    Location:
    Lowville, NY
    This is very timely post for me. I pulled mine off after ridding the bike of the emissions crap and doing a valve adjustment and replacing the carb vents, etc. , and it's smoother but feels slower. That may be an illusion...gonna have to put it back on and set it up properly and see the difference...now that I know how.

    Great post...Thanks!

    *edit* This really should be added to Wisdom section.
    #5
  6. Chuckracer

    Chuckracer Jerkus Maximus

    Joined:
    Aug 26, 2007
    Oddometer:
    9,241
    Location:
    Lowville, NY
    Follow up: Yeah, it's definitely slower...doggy. I guess it's not getting any ignition advance? If you give er a handful, it still goes though.

    I just re-installed the wire and set it as per Zuber's excellent instructions, with help from the manual on CD. Easier than I thought it would be. One tip though: as the tanks are off the bike, when you turn the key on the pump starts and blows what gas is left in the lines straight up in the air. If you're standing on the left side of the bike like I was...well, it's laundry time anyhoo. :D

    Stand on the right side of the bike when you do this! :deal


    Haven't had a chance to ride it yet as the weather sucks here today.
    #6
  7. uk_mouse

    uk_mouse Aquatic adventurer

    Joined:
    Jul 20, 2006
    Oddometer:
    1,632
    Location:
    UK
    Zuber you're a gosh darned life saver :)

    I've been chasing a surging problem on my 950 for months now, fiddled with the carbs endlessly, I even checked the TPS.

    BUT ...

    The repair manual says the TPS should give .5-.6 volts when closed and 3.6 when fully open. Mine seems to have a slightly wider range, so I had guessed that the open voltage was the important one, and set it so that the range was about 0.4 - 3.6. How wrong I was! So now I've adjusted it to give 0.6 closed and about 3.8 open. What an improvement. The surging was not terrible but it was enough to make it very annoying when riding at low speed round town for example.

    So thanks for that info :)

    Also, the repair manual says measure the voltage between the blue and yellow wires, however on my bike it's the blue and black wires that give this voltage. Mine's an early bike (2004) maybe they were wired differently.
    #7
  8. ktm950se

    ktm950se Banned

    Joined:
    Jan 7, 2007
    Oddometer:
    1,385
    Location:
    Southern Maine
    Nice find!

    ktm950se
    #8
  9. Zpider

    Zpider Adventurer

    Joined:
    Jan 12, 2008
    Oddometer:
    98
    Location:
    Sweden
    So the conclusion is that carb bikes DO need the TPS after all. Mine is broken, just sits there and give way false readings in voltage, but i cant really tell if the bike runs as it should, all i know is that it runs ok. I can however feel that its not that crisp in the range of 3000 - 4000 rpm. Maybe time to get a new TPS after all....
    #9
  10. Chuckracer

    Chuckracer Jerkus Maximus

    Joined:
    Aug 26, 2007
    Oddometer:
    9,241
    Location:
    Lowville, NY
    I think so. I ran mine without one at all and it was kinda doggy at lower RPM's, but very smooth - NO throttle jerkiness what so ever. That tells me it was mis-adjusted before...well, I'm sure it was cause I was messing with the idle setting constantly.

    Valve adjustment, carb sync, fuel screw adjustment and replacing the vent lines and it's never run better. The idle is consistant now. I put the TPS back on after seeing this post and set it up, and got the low RPM response back without the snatchiness.
    #10
  11. men8ifr

    men8ifr Been here awhile

    Joined:
    Jan 28, 2008
    Oddometer:
    383
    Location:
    Midlands UK
    Please post on here if you notice any fuel economy differences when the TPS is back workign again, I'm interested in this.
    #11
  12. tejaspuke

    tejaspuke Adventurer

    Joined:
    Nov 14, 2007
    Oddometer:
    28
    Location:
    Tejas

    Mine bike is an 06. The blue and yellow wire voltage was 4.3v closed and 1.3v fully open. I checked the blue and black and the voltage is .6v to 3.6v. Thanks for the tip! :clap
    #12
  13. adiablolex

    adiablolex Lost again

    Joined:
    Jul 30, 2007
    Oddometer:
    3,692
    Location:
    Third rock from the Sun
    same on my 04 I thought the sensor was busted initialy but I guess not.
    black and blue it is
    :freaky
    #13
  14. Problem0

    Problem0 Adventurer

    Joined:
    Oct 2, 2005
    Oddometer:
    28
    Just a word of caution - When you set the TPS up in a cold garage, make sure the carb heaters are disconnected, as they suck a bit of voltage and could leave you with a flat battery: or if you have no fuel in the carbs they could damage the seals leading to a fuel leak when reconnected and then catch fire when you try and balance the Carbs.

    please don't ask me how I know.....
    #14
  15. adiablolex

    adiablolex Lost again

    Joined:
    Jul 30, 2007
    Oddometer:
    3,692
    Location:
    Third rock from the Sun
    *correction*
    black and yellow :huh WTF?
    #15
  16. Farscape

    Farscape Oh, look! A Starbucks!!

    Joined:
    Aug 20, 2005
    Oddometer:
    559
    Location:
    Kickin' stones down the road to hell - Edmond, OK
    Okay, mine's different... But okay. I guess.

    I measured my voltage today. .53v - 3.67v smooth.

    BUT!!! This was measured between the BLACK and YELLOW wires!!! (like adiablolex?)

    I could not get a correct reading between the BLUE/BLACK or BLUE/YELLOW wires :huh

    2004 950 Adv. Mfg. 12 / 2003 if it matters to anyone...

    I'm not sure what this means... But I'm puttin' her back together and moving on. :clap
    #16
  17. adiablolex

    adiablolex Lost again

    Joined:
    Jul 30, 2007
    Oddometer:
    3,692
    Location:
    Third rock from the Sun
    must be an 04 thing...

    can anyone else with an 04 confirm?
    :ear
    #17
  18. Zuber

    Zuber Zoob

    Joined:
    Sep 28, 2004
    Oddometer:
    2,730
    Location:
    Main Street, Shedd, Oregon
    Yes, Black and Yellow wires on all KTM's.

    The early manuals were worng with the Blue/Yellow.

    I edited the original post above.
    #18
  19. bomose

    bomose Long timer

    Joined:
    Jul 22, 2007
    Oddometer:
    2,046
    Location:
    Dixie
    I'm having a surge at about 70 mph. The needle has been raised. I checked my TPS and got a reading of .562 closed and 3.72 WOT. At about half throttle the meter would say off or no reading. That would be about the 70 mph mark. Would you say the TPS is bad or do they all read like that? I am new to the 950 and am having to learn a lot.:huh
    #19
  20. cpmodem

    cpmodem Orange Caveman

    Joined:
    Nov 29, 2004
    Oddometer:
    7,103
    Location:
    masa yee yah tee 59° 14' 9" N / 135° 26' 42" W
    The reading should be linear through the full range of throttle motion. No place should it drop to zero. make sure you are making good contact with the meter probes. You may have a faulty TPS. It happens.
    #20