Speedo and Odometer not working

Asked by Mar 07, 2014 at 06:30 AM about the 2004 Subaru Forester X

Question type: Maintenance & Repair

Hi Im looking at buying an 2004 Forester and apparently the speedo and the odometer are not working. I realise that this is not a particularly difficult fix in other cars but my main question is if these are not working will the digital mileage clock tick over regardless? They aparently have not worked in atleast 4 years?

1 Answer

40,545

Many vehicles use a standardized communication protocol, called SAE J1850, to enable all of the different electronics modules to communicate with each other. The engine control unit counts all of the pulses and keeps track of the overall distance traveled by the car. This means that if someone tries to "roll back" the odometer, the value stored in the ECU will disagree. This value can be read using a diagnostic computer, which all car- dealership service departments have. Several times per second, the ECU sends out a packet of information consisting of a header and the data. The header is just a number that identifies the packet as a distance reading, and the data is a number corresponding to the distance traveled. The instrument panel contains another computer that knows to look for this particular packet, and whenever it sees one it updates the odometer with the new value. In cars with digital odometers, the dashboard simply displays the new value. Cars with analog odometers have a small stepper motor that turns the dials on the odometer.

2 of 2 people found this helpful.

Your Answer

Subaru Forester Experts

  • #1
    Nick Eidemiller
    Reputation
    3,800
  • #2
    walth
    Reputation
    3,150
  • #3
    lifeson34
    Reputation
    2,600
View All

Related Models For Sale

Used Subaru Outback
388 Great Deals out of 36,682 listings starting at $995
Used Honda CR-V
873 Great Deals out of 55,045 listings starting at $1,007
Used Toyota RAV4
905 Great Deals out of 60,654 listings starting at $1,690
Used Subaru Impreza
210 Great Deals out of 18,416 listings starting at $1,500
Used Subaru Legacy
229 Great Deals out of 13,681 listings starting at $900
Used Toyota Highlander
465 Great Deals out of 25,378 listings starting at $2,299
Used Ford Escape
1,134 Great Deals out of 85,571 listings starting at $999
Used Toyota 4Runner
241 Great Deals out of 21,786 listings starting at $1,500
Used Subaru Impreza WRX
54 Great Deals out of 1,287 listings starting at $3,365
Used Toyota Tacoma
566 Great Deals out of 42,425 listings starting at $2,999
Used Honda Civic
843 Great Deals out of 78,708 listings starting at $888
Used Honda Accord
1,045 Great Deals out of 63,027 listings starting at $999

Used Cars For Sale

2018 Subaru Forester For Sale
21,869 listings starting at $22,063
2017 Subaru Forester For Sale
37 Great Deals out of 3,295 listings starting at $19,794
2016 Subaru Forester For Sale
82 Great Deals out of 1,241 listings starting at $15,500
2015 Subaru Forester For Sale
110 Great Deals out of 2,722 listings starting at $6,950
2014 Subaru Forester For Sale
50 Great Deals out of 1,324 listings starting at $8,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.