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Still working on my dead speedometer/no odometer increment problem.

This morning I disconnected the negative battery terminal and unbolted, sanded clean & shiny, and rebolted up all the ground wires I could find in the engine compartment. No change.

Took the cluster out and checked to ensure all connectors are in tightly. Reseated every connector under the dash I could get to. No change.

My buddy and I plugged in a live-data scanner and went on a drive. TPS works fine. Vehicle speed stayed at zero the entire drive.

So... my question: does the signal going from the VSS to the OBD-II port run through the cluster first or directly to it? I'm trying to figure out if (with the diagnostic showing zero mph) that means that the VSS and/or wiring to the OBD-II port are bad, or if the speed signal to the OBD-II port is fed from the cluster (perhaps further implicating the cluster as the bad culprit).
 

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I don't have a good technical answer for you but here is what I noticed with the OBD-Link that pairs with my phone. My SV came with 265/70 tires and the dash-speed was a little off showing me going faster than my GPS and faster than the OBD readout, but the GPS and OBD were spot on in agreement... I then installed a set of 265/75 tires which from reading here I was told would make my dash-speedo spot on, and it did in that my dash-speedo and GPS are in perfect agreement with each other, but the OBD speed no longer matches the GPS or dash-speedo.... I'm hoping that this can be corrected by the dealer entering in a different tire height number into the OBD-Computer...
 

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I don't have an answer, but if you know someone who can read a wiring diagram, I think they would be able to answer your question. The Haynes manual has decent wiring diagrams. That is one thing I would like to learn to do, how to read wiring diagrams.
 

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The OBD II diagnostic port gets it's speed info from the ECM, which gets it's information from the cluster, which receives it's signal from the vehicle speed sensor. The speed sensor generates an AC voltage signal (approximately 1 volt per 10 MPH), which is sent to the cluster where it is converted. Then it'll relay that info to the ECM and, as applies, TCM. First gen Frontier clusters (a.k.a. "integrated meter assembly") are notorious for failure and there are several places that repair them (Circuit Board Medics, Mr. Whizard). The first thing I would to is get the drive wheels supported off of the ground to run the vehicle in gear. The VSS can be unplugged and a multimeter in AC volt setting can be connected to the two terminals, which will tell you if the sensor is sending a signal. If it is, they you have to check if the signal is getting up to the back of the cluster.
 
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