YellR.com Yellow Box speedometer recalibrator installation guide

ba$$fan

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When I got my 2000 GTS, I was unaware that the car had 3.73 gears. I didn't see the car before purchasing and went on the PPI of a recommended viper tech. He apparently didn't notice the speedometer was way off. First drive I'm thinking boy it doesn't feel like I'm going 80. So...first of my lists of todo's for the car was to get the speedo corrected. To verify the gearing change, I jacked the car up and rotated the tire once counting the driveshaft rotations (3.73 driveshaft rotations to one tire rotation = 3.73 gears). I also verified that it was 22% off speedometer vs GPS speed.

After a lot of searching online, I decided to go with the Yellow Box recalibrator. It is priced right, gets great reviews, and has a large following in the sportbike realm. Unitrax is also now selling this unit.

I took some photos and thought I would share the steps required to install the Yellow Box on a Gen 2 Viper. Not sure how much different the others gens are but it's a very easy installation regardless. It would be possible to fabricate some connectors so that you didn't have to cut/splice in wires but I didn't much care about the couple connections that were necessary.


Tools/Supplies Needed:

5/16” socket/driver
Philips screwdriver
Wire cutter
Wire stripper
Utility Knife
Solder
Soldering Iron
Electrical Tape
Heat Shrink Tubing
Lighter

Installation Instructions:

Remove PCM cover bolts using 5/16” socket and a philips screwdriver for the two screws at the bottom.

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Unplug three Power Control Module (PCM) wiring harness connectors. Keep in mind the colors to know proper re-installation placement. Left to Right: Black, White, Gray. The “colored” part of the connector comes off with it. There are squeeze tabs on the top and bottom to remove. Be gentle and don't break them.

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On the black PCM connector wire bunch, find the Dark Blue/Gray striped wire (Pin 2). This is a fused ignition switch output which will power the Yellow Box unit.
On the black PCM connector wire bunch, find the Black/Light Blue striped wire (Pin 4). This is a sensor ground and will be spliced to the Yellow Box unit's ground.

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On the White PCM connector, find the White/Orange striped wire (Pin 28). It is easy to see as it has a separate connector right before the PCM connection. This is the vehicle speed sensor signal, and carries the signal that will be modified by the Yellow Box unit.

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Remove the tape and pull the wire bunch mesh wrapping back so you have room to work right next to the PCM connectors.
Using the wire strippers, remove half inch or less of the Dark Blue/Gray striped wire insulation close to the black connector, but giving enough room to work. Do not cut this wire. It is stranded, so be careful not to cut through the wire when removing the insulation.
Do the same to the Black/Light Blue striped wire. Again, this wire is not cut.

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Cut the White/Orange striped wire before the little single connector that it has. Make sure to leave enough room to connect the Yellow Box wires.

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The wiring harness to the Yellow Box unit has fairly long wires. You may want to shorten them so as to not have too much excess. Also if you are using heat shrink tubing, cut those to length and slip them over each of the Yellow Box wiring harness wires at this point.
Using the soldering iron, solder the Red Yellow Box wire into the exposed area of the Dark Blue/Gray striped wire.
Solder the Black Yellow Box wire into the exposed area of the Black/Light Blue striped wire.
Solder the White Yellow Box wire to the cut White/Orange striped wire on the side is coming from the main bunch of wires that feeds the PCM. This is the input to the Yellow Box from the speed sensor.
Solder the Gray Yellow Box wire to the cut White/Orange striped wire on the side that goes into the connector. This is the output from the Yellow Box that feeds the PCM the corrected speed signal.

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Wrap connections with temporary electrical tape. The Yellow Box is fully wired in and ready to be tested. Secure it somewhere so that you can make adjustments if necessary. If you already know the ratio your speedometer is off, set the appropriate dip switches at this point.
Replace the three PCM connectors.

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Take a drive with GPS and verify correct speedometer reading. If reading is not correct, adjust dip switch settings until it is.

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Back in garage, remove the PCM connectors again and the temporary electrical tape that was over the exposed wires.
Move heat shrink tubing over the exposed wires and apply heat source to shrink tubing until snug.
Secure the Yellow Box unit and plug the PCM connectors back in.

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Reinstall the PCM cover.
You're finished.

And of course the disclaimer: These are the steps that I took in installing this unit, I am in no way responsible if you screw it up. :)
 
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dave6666

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great information, I wonder if the process is applicable to the unitrax calibration box?

I have one from last year that they supplied with my 3.73 OSG unit. They instructions include some wording along the lines of if this wire doesn't work try this wire to the PCM. Yeah...

I've never installed it based on that even after talking to them about it on the phone. I will be doing this mod instead. Didn't see anything wishy washy.

In related news, I have a NIB Unitrax w/ instructions :D
 
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ba$$fan

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They instructions include some wording along the lines of if this wire doesn't work try this wire to the PCM. Yeah...

I've never installed it based on that even after talking to them about it on the phone. I will be doing this mod instead. Didn't see anything wishy washy.

The wire they are probably talking about is the speedo sensor connection. There is one wire that is the speedo sensor input into the PCM and there is one that is the output to the actual speedometer. Seems different versions of the old Unitrax box had different instructions saying use on or the other. I used the input into the PCM, as that made more sense to me...telling the PCM actually how fast the car is going. It works, so it must be right!
 

JonB

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I have one from last year that they supplied with my 3.73 OSG unit. They instructions include some wording along the lines of if this wire doesn't work try this wire to the PCM. Yeah...

I've never installed it based on that even after talking to them about it on the phone. I will be doing this mod instead. Didn't see anything wishy washy.

In related news, I have a NIB Unitrax w/ instructions :D

Unitrax instructions where provided due to the varying Voltage issues of the various models/years of Vipers. Unitrax has done 20X more than anyone. Cmon.....
 

JohnnyViper

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i got the old style with my kinda recent (3 months ago) purchase of gears, i will give it a try, seems to have been proven in the field if you get it hooked up right
 

dave6666

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Cmon.....

C'mon what?

Problem 1... Use pin 28 but if it doesn't work call us.

Problem 2... Use pin 27 if 28 doesn't work but call us before you do that.

Problem 3... Make sure it works before you really install it.

Problem 4... Problem 1, 2 and 3

It's not like this thing is being spliced in to the computer for your entire car.

:rolleyes:

I have nothing against Unitrax. I do have something against this. I need one full click up the warm fuzzy food chain before biting in on this product.

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JohnnyViper

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ya, maybe i should buy the yellow box, that unitrax is money down the drain, those instruction do not inspire confidence :rolleyes:
 

Ratical2

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Thanks for the right up. It helped quite a bit. Got mine done tonight. Devin at Unitrax preset it for 3.55's and took all of the guess work out of it. It was dead on. Thanks Devin!
Once you have done it once, you could probably do the whole installation in 15-20 minutes. This does not include the test drive or any minor adjust.
 

freck_d

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can any one here tell me what they have there dip switches set to? 98 viper with a 3.73
 
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