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I must admit to not being an electrician and give all the credit to Modfry who sent me detailed instructions with a labeled color picture.
We powered in on a yellow wire (there is more than one) with a t-tap, grounded under the bolt that holds the hood release lever and cut the blue/white speedo wire for the other connections.
Actually the wires are not in the ECU but go to the light blue C101 connector a few inches below the ECU. The wires you want are in a taped bundle that exits the C101 connector. If you can get Modfry to post the info it would be helpful to everyone.
The blue/white speed signal wire leaves the speed sensor on the tranny and runs through connector C101 (behind driver's foot well, closest to the dead pedal) and then SOMEWHERE (over the rainbow??) it splices with another blue/white wire that goes to the ECM. The original blue/white wire continues to the speedometer.
The point is that putting the yellow box at the ECM will NOT adjust the speedometer, only the ECM.
I don't know what pisses off the ECM, but it could be any of these:[list=1][*]missing speed signal (good chance of this)
[*]sees an altered speed signal (I don't mean speed-corrected, I mean different voltage)
[*]sees a speed signal that is different than one it senses somewhere else (I don't know where, I'm guessing)[/list=1] Remember that because of the way the blue/white wire is T-tapped, the speedometer could work fine, but the signal to the ECM could be screwed up by an improperly installed yellow box. That may explain the CEL some people are getting. Then again, it's also possible that the yellow box does something to the signal that the ECM doesn't like, in which case you should only put the yellow box in the speedometer wire. But since all you want to change is the speedometer anyway, why fool with the ECM?
I do know that I've cut and spliced my wire and spent quite a while playing with a home-made "yellow box" and never once had the CEL come on. I believe where I spliced ONLY modifies the signal seen by the speedo and leaves the ECM alone, but I've not traced it out. But it doesn't matter - where I (and Sideways) spliced WORKS.
Here is the pic I sent to Sideways. The blue/white wire is the speed signal, the yellow one is +12v power. If you want the regulated power wire that feeds the speed sensor (instead of +12v), grab the yellow/blue wire in C101.
Man, why go through all that wire spaghetti when it's so easy to do this right off the sensor on the tranmission case? There's no risk to the ECU or that the CEL will come on.
Doing it the ECU way is taking a very easy job and making it way too complicated.
[QUOTE]Originally posted by Rick Hesel
[B]Man, why go through all that wire spaghetti when it's so easy to do this right off the sensor on the tranmission case?
When you change to the 4.44 gears you must be careful about hitting the rev limiter. It really sneaks up on you quickly. My experience shows Modfry's shift indicator is the greatest at warning you when to shift without taking your eyes off the road. It has kept me out of the fuel shutoff (face in the windshield) condition since I installed it. A must have item if you like to redline it.
Thanks Sideways...I've been looking at different shift indicators, I have a slight hearing problem so I'm considering an aiudio shift timer with a beeper mounted in the headrest..as well as a visual. Now if I can just figure it all out...lol
fltsfshr
04-26-2003, 09:53 AM
condition since I installed it. A must have item if you like to redline it. 
