Meant to post this a few nights ago but ended up working late and then focusing on a damaged PCB for a relay box I'm refurbishing...
In this thread (1988 FJ62 MAF Suggestions - https://forum.ih8mud.com/threads/1988-fj62-maf-suggestions.1250616/) there was brief discussion of a VSS in the FJ62. When first mentioned my immediate thought was the typical VSS mounted to the transfer case and used to drive an electronic speedometer, which the 6x series doesn't have. Then at the mention of a VSS inside the speedometer, I was still certain that that wasn't the case as my speedometer (a US spec 1/88 FJ62) lacks the 4-pin connector on the back (or so I thought it did, as it was only cheap parts store terminals on the light wires and that was it). Also, my 1988 repair manual (pub RM080U) makes zero mention that I could find of a VSS in any section or in the wiring diagrams. When @RockDoc and @Engineer8000 posted pics from their manuals needless to say I was pretty surprised. I then dug and found pics I took of the innards of my speedo when I cleaned it out a couple years ago. When I took a closer look, I noticed a rudimentary magnetic sensor inside connected to the (unused in my truck as it was connected nowhere behind the dash, and was finally secured out of the way by me when I cleaned out the wiring and added a Weatherpack connector for the lighting) green/black wire and ground wires that were screwed through the back of the speedo housing. This got an emphatic "Whale oil beef hooked" out of me at that point. Next time my dash is apart I'm going to check it out more in depth.
It was stated in the aforementioned thread that this sensor is believed to be four pulses per revolution. Given the single wire coming off of mine and not that 4-pin connector I've seen mentioned, I wonder if mine really even does anything at all. Since I can't leave anything alone, I'm going to connect a portable oscilloscope to it and see if I can find any kind of signal generated by it or not as my truck is driven. There really is nothing to gain as far as anything I'm doing that would take advantage of it if it actually functions, and if my ECU even has a connection for it (which according to my FSM it doesn't) it's ran all these years without it connected and never threw a code on the CEL.
This all makes me wonder if a functioning VSS inside the speedo (ie: one that has the 4-pin connector) may have been specific for more stringently smog controlled areas such as California or similar areas. I only wonder this because of my ECU never having any problems related to any VSS signal nor is one called out in the FSM I have.
Edit: The more I think about this and look at the first picture, the more I wonder if the pigtail coming off my speedo from the factory had four pins and was just hacked away by the time my old man got the truck in 1990.
In this thread (1988 FJ62 MAF Suggestions - https://forum.ih8mud.com/threads/1988-fj62-maf-suggestions.1250616/) there was brief discussion of a VSS in the FJ62. When first mentioned my immediate thought was the typical VSS mounted to the transfer case and used to drive an electronic speedometer, which the 6x series doesn't have. Then at the mention of a VSS inside the speedometer, I was still certain that that wasn't the case as my speedometer (a US spec 1/88 FJ62) lacks the 4-pin connector on the back (or so I thought it did, as it was only cheap parts store terminals on the light wires and that was it). Also, my 1988 repair manual (pub RM080U) makes zero mention that I could find of a VSS in any section or in the wiring diagrams. When @RockDoc and @Engineer8000 posted pics from their manuals needless to say I was pretty surprised. I then dug and found pics I took of the innards of my speedo when I cleaned it out a couple years ago. When I took a closer look, I noticed a rudimentary magnetic sensor inside connected to the (unused in my truck as it was connected nowhere behind the dash, and was finally secured out of the way by me when I cleaned out the wiring and added a Weatherpack connector for the lighting) green/black wire and ground wires that were screwed through the back of the speedo housing. This got an emphatic "Whale oil beef hooked" out of me at that point. Next time my dash is apart I'm going to check it out more in depth.
It was stated in the aforementioned thread that this sensor is believed to be four pulses per revolution. Given the single wire coming off of mine and not that 4-pin connector I've seen mentioned, I wonder if mine really even does anything at all. Since I can't leave anything alone, I'm going to connect a portable oscilloscope to it and see if I can find any kind of signal generated by it or not as my truck is driven. There really is nothing to gain as far as anything I'm doing that would take advantage of it if it actually functions, and if my ECU even has a connection for it (which according to my FSM it doesn't) it's ran all these years without it connected and never threw a code on the CEL.
This all makes me wonder if a functioning VSS inside the speedo (ie: one that has the 4-pin connector) may have been specific for more stringently smog controlled areas such as California or similar areas. I only wonder this because of my ECU never having any problems related to any VSS signal nor is one called out in the FSM I have.
Edit: The more I think about this and look at the first picture, the more I wonder if the pigtail coming off my speedo from the factory had four pins and was just hacked away by the time my old man got the truck in 1990.
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