Speedometer Correction

Discussion in '348/355' started by Gargamel647, Nov 8, 2021.

  1. Gargamel647

    Gargamel647 Rookie

    Apr 11, 2021
    Las Vegas
    Full Name:
    Vincent Vitale
    I know this has probably been done before but I figured being I needed to do it, I would try to make a picture friendly thread.
    I recently changed the tires on my 1990 348 to a shorter tire on 360 wheels. 215/40/18 Potenza RE-71R and 265/35/18 Potenza Sport.
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    This cause my speedometer to read 50mph when I was doing 43mph on my GPS. I purchased the speedometer correction kit from 12o'clock labs. Below are the parts I purchased.
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    Here are the instructions that come with the kit. The kit will have 4 wires you need to connect. RED, BLACK, GRAY and ORANGE.

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    Start by removing the gauge cluster. There are to screws that are on the bottom. The picture will show the attachment point for the screws after they are removed. Then you simply lift from the bottom and unhook the top and unplug the connectors.
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    This 5 pin connector is the speedometer connector.

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    About 5 inches from the connector I cut the red/black wire (second pin the speedo connector).

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    You connect the GREY wire to the RED/BLACK (from the speed signal end) and the ORANGE to the RED/BLACK )going to the speedometer connector.
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    Cut the GREEN/WHITE wire on the same speedometer connector harness and splice the RED wire to it.

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    Then I grounded the BLACK wire to a contact point behind the cluster.

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    Then reassemble and program the kit to following instructions.

    My GPS said I was going 43mph but the speedo was saying 50mph.
    (43/50 * 100) - 100= -14.0

    -14.0 is what I need to program to the unit.

    Here is the video link to program it.

    SpeedoDRD v3.8 and v4.0 Setup - YouTube

    It worked perfectly and it is a 35 minute job if you do not suffer from "Analysis Paralysis".
    Yassa and Qavion like this.
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  3. KevZep

    KevZep Formula Junior

    Feb 17, 2020
    New Zealand
    Full Name:
    Kevin Bennett
    Awesome, thanks for posting this, I think I am going to do this to mine, it reads about 5kph over what the car is actually doing, this is the fix!!
    Great stuff!!
    Gargamel647 likes this.

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