Hi I need help with a speedometer problem on my 2000 Maxima SE A/T. I've done as much research as i could but I'm close to giving up on the problem. I'll try to be as detailed as possible so please bear with me. 3 or so months ago I bought the car from an independent shop, the car was listed as having 3 electrical problems including the speedometer not working. I fixed the other 2 but the speedometer is something that has been very hard for me to diagnose. I found out my car was supposed to have a speed sensor on the transmission besides the revolution sensor, it is indicated the transmission had been replaced for one of a 2001 year car, so I bought the speed sensor and the wiring harness for the sensor at a dealer, after that i tested the speed around the neighborhood and it seemed to be working as opposed to before. I was WRONG... as soon as I took the car into the highway I noticed that once reached around 55 mph the speedometer needle would start dropping the faster I went, then when I reduced my speed it would go back up to the speed where it started dropping and down again, working normally. then it occurred to me that MAYBE the instrument cluster had also been replaced for a newer one since it only had 90k miles on it, so I went on ebay and got one that I thought would be the right fit for my car. the description seemed to be right, plus it had over 200k miles. Once it arrived I switched them over and NOTHING I had the exact same problem! so I decide, that possibly I had a defective speed sensor to begin with, so I went and bought another one from Autozone just to test the theory, guess what?... same problem, I've read as many wiring diagrams as I could get off AllData and Mitchel on demand, but i feel I have reached a dead end for I have tested almost every component part of the speedometer,(excluding ECM, TCM) next I connected a Genisys Evo(scan tool) to the car, and drove around while checking the following inputs: all 4 wheel speed sensors, Vehicle Speed sensor, Engine Speed, Transmission Gear, TPS voltage and %. all looked normal as they were reading around the same speed BUT I noticed something weird one of the data lines reading "Vehicle Speed Engine read my speed correctly at times for example 72 mph then suddenly would drop to 23 mph. now keep in mind this wasn't the signal coming from the transmission's Vehicle Speed Sensor for this one was labeled "Vehicle Speed Transmission" and its reading was always at a steady speed. So that is my dilemma, What could I be missing? Is it possible the cluster I bought was also wrong? if so how do I identify if the cluster is the exact model I need for my car? and Where does the reading for vehicle speed Engine signal come from? I need a very detailed explanation to how the reading on the cluster is calculated. P.S i did some basic resistance testing of some of the wiring from from the VSS to the cluster and to the TCM, but it seems to be ok, is there a better way of testing the wiring? Any help is appreciated.