ba$$fan
Enthusiast
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.
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.
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.
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.
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.
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.
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.
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.
Take a drive with GPS and verify correct speedometer reading. If reading is not correct, adjust dip switch settings until it is.
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.
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.
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
You must be registered for see images attach
Take a drive with GPS and verify correct speedometer reading. If reading is not correct, adjust dip switch settings until it is.
You must be registered for see images attach
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.
You must be registered for see images attach
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.
Last edited:
