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Thread: Incorrect Speedo reading TD5 D2a Auto

  1. 31st January 2017, 07:48 PM #1
    TAHAIC
    TAHAIC is offline Fossicker
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    Incorrect Speedo reading TD5 D2a Auto

    My D2 has had this problem since I bought it over a year ago. Tyre size is only 5% over but my actual speed is 10% over. I bought a nanocom and it says road speed under instrument menu is 10% higher than my speedo in my dash - when I check road speed in the nanocom TD5 engine menu it agrees with my dashboard speedo. I have checked my actual speed against those smiley face signs on the side of the road and my real speed is 10% higher than my dash speedo.I have also confirmed my factory tyre size with land rover using my VIN number.

    Does anyone have any suggestions or ideas as why this is happening? It is definitely affecting the gear changes with higher speeds (10% from dash) required to get into top gear. I have a fuel economy problem which I think this added to but is not the main cause. Any help would be appreciated.

    TAHAIC
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  2. 31st January 2017, 08:26 PM #2
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    Scouse
    Scouse is offline OldBushie Gold Subscriber
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    I don't know why your speedo is under reading that much. It should over read slightly with standard tyres (235/70/16 or 255/55/18). What size tyres do you have now?
    Does it return to 0kph OK when stopped (maybe the needle has moved on the shaft)?

    My Nanocom was out like yours too, one screen said x kph speed, another screen y kph. I had to go into Tyre Coefficient to get it right.
    Scott
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  3. 31st January 2017, 08:54 PM #3
    twr7cx
    twr7cx is offline YarnMaster Supporter
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    Fit one of the speedo correction modules, adjust it to be correct and worry no further?
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  4. 31st January 2017, 09:01 PM #4
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    Rok_Dr
    Rok_Dr is offline Wizard
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    Firstly have you checked it against a gps unit?

    And second what size tyres are you running? I'm running 245/70R16 and the speedo is spot on, 100kph is 100kph true.

    Cheers

    Steve
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  5. 31st January 2017, 09:47 PM #5
    strangy
    strangy is offline ChatterBox
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    What tyre size are you running?
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  6. 1st February 2017, 07:08 AM #6
    TAHAIC
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    I have 265/60 R18's - my D2 came out with R18's

    When my dash speedo say 100km I am actually doing 110km.
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  7. 1st February 2017, 09:43 AM #7
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    John_D4
    John_D4 is offline ChatterBox Subscriber
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    I think I'd just buy a speedo correction box, marks 4wd used to sell them, and end my issue that way. Then you could put any size u like on it next time.
    "Land Rover - making mechanics out of everyday motorists for nearly 70 years"
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  8. 1st February 2017, 09:51 AM #8
    Mk1_Oz
    Mk1_Oz is offline Master
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    Do these boxes only change the signal sent to the speedo or does it make changes to the signal into the ECU? People have mentioned issues with gear changes. Changing the speedo reading only would presumably not alter the gear change issue.
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  9. 1st February 2017, 11:08 AM #9
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    John_D4
    John_D4 is offline ChatterBox Subscriber
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    By memory u can alter the speedo by %

    This kind of idea

    http://www.marks4wd.com/speedo-correction/mfk2800u.html
    "Land Rover - making mechanics out of everyday motorists for nearly 70 years"
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  10. 1st February 2017, 07:29 PM #10
    strangy
    strangy is offline ChatterBox
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    Here is some light reading.
    https://www.aulro.com/afvb/discovery...on-d2-32s.html
    I have the c1600 unit.

    The D2 auto has a speed sensor for the output shaft speed which is interpreted by the EAT ECU and compared with engine speed from the engine ECU .
    These signals are used for determining shift points.
    The SLABS ECU takes the signals from your wheel speed sensors which then inputs the BCU for numerous
    speed related functions and then to the speedo.
    The speed correction unit interfaces between the SLABS and BCU.
    This is the signal you need to correct.
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