About to run a new wire from the speed sensor to the ecu to fix my no speed or odometer issue i believe I've found it on the ecu now which wire runs from the ecu for the speedometer reading? It's a 93 ls400 ive already relaxed both speed sensors swapped gauges and ecu's and still getting code 42

 

Not sure if you got to fix it or not, but I saw multiple occasions of no Speedo/odo/mpg gauge on IS300/GS400, people would replace abs sensors and still get no signs of life on the speedo and odo. Jumping the pins shown in the image would activate self diagnostics mode once the key is turned to ON position. Dash would light up with all it's bulbs blinking. If you have a check engine light you can read it by counting how many times it blinks, but more importantly there's a sequence to reset ABS codes which can't be reset by disconnecting the battery. In self diag mode you have to press brake pedal 8 times as quick as possible. After that ABS light would stop blinking. Take out the key, take out the jumper start the car enjoy the speedo. Again of course this worked for me on a 98 GS300 2000 GS400 and 2002 IS300 with faulty ABS sensors. Depends on your wiring might be worth a try .

 

Yeah with mine being a 93 LS400 I doubt that will work I found about three different wires that go to my ECU that could be for the speed sensor but it's hard to tell exactly which color it is I've tried applying voltage to the wire down to the speed sensor to find the correct one but it's not working yet unless that wires broke somewhere