I installed the box yesterday, the hookup is pretty straightforward, but the calibration is tricky. It was difficult to figure out how to input the correct ratio, but now the speedometer reads correctly, and it is possible to calibrate it very precisely.
There is a writeup by another guy on
4x4wire who installed the same box on a Tacoma, but he tapped into the wires at the sensor under the truck. Rather than run new wires through the firewall etc., I thought it would be a little more sanitary to find the wires inside the cab and tap them there.
They run through the firewall in the big boot on the passenger side, and come out behind the glove box. The wires are a pink, light blue and green with red stripe. I found them at a connector above the glove box liner.
Glove box removed:
Glove box liner pulled down (don't mess with any yellow connectors, that's the airbag!!):
Here you can see the pink, blue and green/red wires (blue=ground, pink=power, green/red=signal):
For the connection, I used a multi-conductor cable that I cut from an old CD-changer control. I gave it about 3' of length, so I can have the box close to me for calibration while driving.
One end of the cable goes to the box. I used the same colors as the sensor, and red for the output to the speedo. This photo shows the output connected to Output 1, but for the Tacoma I had to move it to Output 2.
The green/red wire from the sensor gets cut, and the sensor side goes to the box input, and the speedo side goes to the box output. The pink and blue just get tapped onto for power.
That's about it for the hookup. There is a big table in the instructions you need to use to find the correct coarse and fine settings, and the lights on the box will flash a certain number of times to indicate what the setting is. RTFM, it is a little unclear. For my correction of 15%, the coarse setting flashed 15 times, and the fine flashed 10. All the DIP switches are set to OFF.
Once you get all that stuff sorted, you can start driving and use GPS to dial in the speed. If it reads too fast, hold the DOWN button, and as you drive at a steady speed you will see the speedo needle VERY SLOWLY drop. It moves maybe 1 mph for every 2-3 seconds you hold it down. Once you are happy with the calibration, find a place under the dash to stash the box and hold it down with screws or velcro. You'll never have to think about it again unless you change tire size.
!