DIY: Marks Speedo Correction Install 2004 100 Series

[DomSmith]

After upgrading to slightly larger tires I decided I wanted to have the most accurate speedometer I could. I searched MUD for write-ups on the speedo correction boxes and found some good info but no definitive step-by-step how to. After reading these two threads:

https://forum.ih8mud.com/100-series...alling-generic-marks4wd-speed-calibrator.html

https://forum.ih8mud.com/100-series-cruisers/211990-installed-superlift-speed-sensor-calibrator.html

I had the confidence that it wouldn’t be too hard, so I made a quick call to Slee and the Marks Speedometer Correction Box was on its way.

The kit comes with the programmable box (with plenty of wire), directions, and some wiring connectors.


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2591/IMG_2591.jpg


There are basically 5 steps once you purchase the unit.

1. Remove the glove box.
2. Locate correct wires and make connections and then test that you’re getting power, etc.
3. Program the box and road test.
4. Make connections permanent.
5. Replace glove box.




STEP 1: GLOVE BOX REMOVAL

The first step was to remove the glove box. Start by removing the two screws at the bottom which loosens the entire assembly...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0064/IMG_0064.jpg



Slide the glove box to the left and pull out on the right side being sure to clear the tab on the right...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0063/IMG_0063.jpg



Next I had to disconnect the lanyard that attaches to the left side of the glove box. This tends to retract up into the dash and may be hard to find once you need to re-assemble. Now the glove box is free to place out of the way.


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0065/IMG_0065.jpg



STEP 2: WIRING (Disconnect battery ground)

Speedo Box wires-

Red (PWR) to switched power source
Black (GRND) to ground
Blue (OUT) to R-G to speedo
Brown (IN) to R-G from loom

Next was locating the appropriate wires to attach the speedo box to the stock wiring harness. The wiring diagram shows the Vehicle Speed Sensor (VSS) passing through connector IX1 before heading to the speedometer. It’s shown as PIN 6 on IX1 and is R-G (Red w/ Green). This is the wire to tap into with the Blue and Brown wires from Marks Speedo Box. From the 2004 EWD...


http://www.dominicsmith.com/100_Ser... AM/Screen Shot 2013-02-27 at 11.31.03 AM.jpg





http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IX1/IX1.jpg



On my 2004 it was found just to the left of the ECM at the bottom of a cluster of plugs (not plugged into the ECM)...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0078/IMG_0078.jpg



It has a push-in fitting at the back of the plug holding it in place, just pull it towards you off its mounting location. This is what it looks like:


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0067/IMG_0067.jpg



Now you can unplug it and CAREFULLY use a razor to cut back the wiring protector to gain better access to the wiring loom...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2569/IMG_2569.jpg



Next confirm you have the right plug. The female side has all Sky Blue wires and the male side you're tapping into has R-G in both PIN 6 and PIN 7. I marked PIN 6 with tape to be sure I didn’t mix up the two...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2570/IMG_2570.jpg


I decided to keep the speedo box out of the glove box because I keep things in there and felt like the toggle had potential to get tripped in there. I opted to Velcro it up under the footwell beneath the glove box where there was room but would not interfere with passenger foot space. I routed the speedo box wires up from that location to the area behind the glove box for the connections...

http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2600/IMG_2600.jpg



Then I cut the PIN 6 R-G wire and connected the brown wire to the R-G wire heading into the loom and the blue wire to the R-G wire going into the rear of the plug. I made temporary wire nut connections for the testing process...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2602/IMG_2602.jpg



http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2603/IMG_2603.jpg



Now I took the recommendation of jhrrld and tapped into the antenna relay wiring (A30) located nearby. There are certainly other wires to choose from but I decided to stick with something that had been confirmed to work...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0077/IMG_0077.jpg



Connecting to “power” with the red wire, I used PIN 7 (B-W) and “ground” I used PIN 5 (W-B).


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/A30/A30.jpg



PIN 7 is switched ON, not ACC so be sure to note that when testing. There’s not a lot of room in that area so making the connections may be difficult. Again I marked each wire with tape to be sure I was connecting to the appropriate wire...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_0070/IMG_0070.jpg


The white tap-in connectors supplied were basically worthless as they aren’t small enough for the wires I chose to tap into. Don't waste your time trying this...


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2601/IMG_2601.jpg


I eventually stripped a small section of each factory wire (without cutting) and wrapped the speedo box wire tightly around them then covered them in tape until testing was complete.


http://www.dominicsmith.com/100_Series_Speedo_Correction_files/Media/IMG_2606/IMG_2606.jpg



Then I re-connected the battery and checked that I was getting 12v to the red wire and confirmed that the green LED came on inside the speedo box when the key was turned to ON. Leave the back cover off for now...

Now you're ready to program and test...
​

 

[DomSmith]

STEP 3: Program and Road Test

The Speedo Box has only a few parts to it.

1. Toggle switch on the front to switch from Position A and B.
2. The Green LED (as seen above) to indicate power.
3. The two digit LED display (shows the calibration digits). Comes on when the buttons are pushed and goes to sleep after 30 seconds.
4. The adjustment buttons (to the right of the display) adjusts the digits for proper calibration.


Here's the front toggle...

You can see the adjustment buttons here in relation to the display...

The instructions say that the box comes pre-programmed for 31” tires as a 1:1 ratio in the A Position preset at "00". To change the box to your tire size you have to program the B Position using the correct ratio. There are common tire sizes pre-written in the instruction chart showing the ratio and the digital setting that corresponds. Basically if you’re running a 33” tire you would use the buttons inside the box to make the display show the proper digits which are “07” per the chart. I’m running BFG A/T KO’s at 285/65/18 which BFG shows as 32.7” actual diameter on their website. The chart lists the ratio for 33” as 1.07 so I knew it would be less than that.

To determine the ratio I wanted to be spot on so I used the following which compares a 32.7' tire to a 31" tire…

A:B=C or (Stupid character smiley faces!!!)
31:1=32.7
In this case D=1.054

Referring back to the chart I rounded up to 1.06 which shows the input needed to be set at “06”. At this point I made sure the A Position was set at “00” and then switched the toggle to B Position. (*The display inside the box does not turn on until you press the up or down button inside the box). Press the up button until the display shows “06”. Now toggle to A Position and back to B to program. Your box is now programmed.

I started my road test in the A Position to see how far off I was from my iPhone GPS App. I was at the same spot before I installed the speedo box, with the speedometer reading approx. 68 MPH at 65. Then I switched to the B Position and realized I was about 2 MPH above my iPhone GPS. This made me realize that the programming is just a start and to dial it in you need someone to change the setting one way or the other with the push buttons inside the box while driving. After the drive adjustments I finally rested on “04” on the display. This cross-references to a ratio of 1.04 in the instruction manual.


STEP 4: MAKE CONNECTIONS PERMANENT

Once I was happy with the settings I wanted to make everything permanently connected and sano. I started by disconnecting the battery again, then removing the wire nuts at the VSS and soldering them together and shrink wrapping...

At the antenna relay there was very little room to work with and since I didn't cut the wires I didn't have the luxury of shrink wrap. I opted to solder the wires and wrap with several wraps of electrical tape. Not the ideal solution but with poor access and not much else to choose from it had to do.

Next I re-wrapped the wire loom at the A30 connector and at the IX1 connector and plugged them back in (be sure to press the IX1 back into it's holder)...

To assure a clean install and help protect the wiring from any chaffing I wrapped the remaining wire in tape. I chose not to cut off any excess wire so it could be easily pulled out to re-program as well as relocated if necessary...

Next I replaced the back cover and fitted the box (toggle up and out of the way) to the under side of the glove box. Once in the best location, I used adhesive velcro (not included) to hold the box firmly in place...

Now I gathered the rest of the wire and zip tied it together and placed it into the nook behind the glove box...

STEP 5: REPLACE GLOVE BOX

Now put the glove box back in reverse order, re-attach the battery and you're done. The lanyard that controls the descent of the glove box was hard to find as it had crept it's way up into the dash a bit for me. I was able to hook it with a screwdriver and stretch it down to get it back in place. Here's the final location of the box...

After just a day of driving I have a few observations:

1. The speedo is definitely a little jumpy form 0-15 MPH. Not bad but noticeable if you're looking.

2. $200 and a bit of work is worth the effort of saving me (or the wife) from a speeding ticket here in CA where fines are big $$$. Not to mention traffic school, insurance rates, etc.

3. I'm also hoping to get actual mileage on my truck and accurate GPS distance and MPG info on the Nav.

4. People with much larger tires should see an even better benefit.

5. It looks like you can program the A Position for any regular set of tires (say 285/65/18 like me) and program Position B for another larger size you may use off-road.



Thanks to jhrrld and pequiod for their posts listed above.

 

[neoworm]

Good write up. Thanks.

 

[Trunk Monkey]

I wouldn't use marettes for your wire connections.

He said it was temporary while he tested things.

Great write up, thanks for the detailed pics. Def. going in the FAQ.

 

[3D FJ]

I just received my speedo correction unit today. I was curious about something. I've seen the writeup for the superlift on a 2000, the one done on a 2006, and this one done on a 2004. The wiring for the 2004 and 2006 are the same with the 2000 being different. I'd like to be able to look at the 2003 wiring diagram to make sure which wire i'm cutting. Where are these diagrams to be found? I've been looking at both my vol.1 and vol.2 FSM's and for the life of me i can't find it. Would this be located in another manual that i don't have?

 

[nnnnnate]

Does this correct only the speedo reading or does it also adjust the mileage? Is the odometer independent of the speedo or are they getting the signal from the same wires?

Thanks.

 

[phi1osopher]

Does this correct only the speedo reading or does it also adjust the mileage? Is the odometer independent of the speedo or are they getting the signal from the same wires?

Thanks.

This is my question too, as I'm looking to experiment installing a cheap-o universal digital speedo-corrector.

 

[DomSmith]

Guys I don’t have this truck anymore to use gps to test the mileage. My apologies.

 

[jLB]

Does this correct only the speedo reading or does it also adjust the mileage? Is the odometer independent of the speedo or are they getting the signal from the same wires?

Thanks.

This is my question too, as I'm looking to experiment installing a cheap-o universal digital speedo-corrector.

I used this thread, for wiring locations, to install a "yellow box" ( Official home page of the Yellow Box Speedo Recalibrator ) speedometer correction box in my son's 2000 TLC.

In our experience, installed at this location, the speedometer correction is for the speedometer and odometer only. Which is exactly what we wanted. It does not adjust the ECU/OBDII speed.

This was verified by:

1) the odometer does not update with the wire "cut"
2) comparing to highway mile markers.
3) comparing to GPS
4) comparing to OBDII speed output (Torque/ScanGauge)​

One caution, according to the EWD (for each of our vehicles), the actual pin on IX1 appears to be different, between my son's 2000 TLC and my 2006 LX.

 

[LandCruiserPhil]

Guys I don’t have this truck anymore to use gps to test the mileage. My apologies.

Again great write up I wish you did more