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  1. #1
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    VOLVO Speed Sensor

    Can anyone tell me where the speed sensor for the speedometer is located on a 2007 Volvo 780?

    My speedometer has quit working most of the time. I want check the connection at each end of the cable/wire if possible before I go to a dealer.

    Any help is greatly appreciated.


  2. #2
    Road Train Member Pablo-UA's Avatar
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    What tranny? if Manual, it is located on tranny tail housing, magnetic type, 2 wires are used.

    It is directly connected to Vecu. If wires are bad ore sensor fails VECU cuts power.

    So check VECU for fault codes.

    If VECU memory is clear check dashboard for J1939 CAN message codes.

    Sometimes small speedo arrow motor inside dashboard fails and arrow wont moving.

    Do you have C/C issues?

  3. #3
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    Pablo, thank you for your reply.

    It is a 13 speed manual transmission. I imagine the sensor is in the same general area regardless of the type of transmission.


    Here are the details/symptoms.

    When the speedometer is not working the following also occurs:

    1) Odometer does not work

    2) Cruise control will not work

    3) Jake Brake does not work

    4) If rpm's go above 1500 engine power is cut back

    So it appears that it is the speed sensor or the wiring. Can still drive the truck with the above limitations. When I called VOLVO I was told if it was the sensor I would have to have the truck towed. Glad they don't know what they are talking about there.

  4. #4
    Road Train Member Pablo-UA's Avatar
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    it is VSS wiring issue. Check the VSS connector on tranny tail first.

    Check output shaft for play, VSS for dirt, oil and pices of metall on it.

    If everething is OK, check wiring



    It is twisted pair. You will easily find it by color under the cabine and inside on VECU connector (I hope you know VECU location). Also check the Chassis-Cabin connector under the hood for corrosion

  5. #5
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    Quote Originally Posted by Pablo-UA View Post
    (I hope you know VECU location).
    Actually, no I don't know where it is. I have had this truck for 3 1/2 months and haven't got that deep into it yet.

    Thanks again.

  6. #6
    Road Train Member Pablo-UA's Avatar
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    to acess the VECU, unscrew and rise fuse board. VECU if a small black box a bit right from center. You can see LCM there too.



    This is Version-II location diagram. There are all units used on Volvo trucks, some of them are used in EU only, like Tachograf, so look for unit you need (#10). And that's why it is a lot of unused room inside dash.

  7. #7
    Road Train Member Pablo-UA's Avatar
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    Have you solved your speedo issue?

  8. #8
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    Quote Originally Posted by Pablo-UA View Post
    Have you solved your speedo issue?
    No not yet.

    Have been busy and now it is raining. Hopefully tomorrow I can crawl under and take a good look. I have contacted a couple dealers along the way this week. All are backed up. I am able to drive the truck so I'm not going to screw up my schedule to wait in line. I am picking up a 900 mile load Friday morning that does not deliver until next Wednesday. So I should have time to get this taken care of one way or another.

    Pablo, thank you again for your help. I will post an update when the situation has been resolved.

  9. #9
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    I got my truck in for repair today. They said that the speed sensor was stuck because it had broken apart and would have to be drilled out to remove it.

    So the bill was $293 to replace a $30 part.

  10. #10
    Road Train Member Pablo-UA's Avatar
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    broken VSS?? Are you sure no output shaft play? no some broken parts inside transmission sensor was hit with??

    This sensor is a small magnet with coil. pices of broken parts may stay in it and it will let pole ring hit the sensor.

    If sensor was drilled out, change transmission oil and filter (if equiped). Yoi may see some surprize in oil

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