Vehicle Speed Sensor

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More info, FJ62 (didn't know that they had VSS), what engine, etc.?

A VSS is a usually an inductive pick-up pointed at a reluctor, sometimes referred to as a "tone ring", that tells the ECU has fast the rear output shaft, or something directly connected to it, is spinning. From that signal it calcs the vehicle speed.
 
If it's like the FJ60s it's not really a VSS - there's a sensor of sorts in the gauge cluster that works off the speedo cable. It's more for emissions, and I have no idea for 62s how it behaves... But I believe there's a description in the FSM.
 
The VSS in a FJ62 is an integral part of the speedometer. It is nothing more than a magnetic reed switch that is activated by the magnets that spin with the speedometer cable. If your speedometer operates correctly, then it might be the reed switch but more likely a bad connection between the speedometer and the ECU. Check the FSM under Body Electrical System - Combination Meter. If the reed switch is bad, the FSM says to replace the speedometer. All you need to do is pull and open up the speedometer and install a new reed switch. You can salvage a reed switch from most mid 80's to mid 90's cars or pick one up of similar physical size from an electronics supply house. They are also used as door closure sensors in security systems. You will just need to remove the plastic enclose to extract the actual reed switch.
 
I'll toss this in as an observation. When I did the 3FE swap into the 60 I retained the 60 speedo and never had any codes thrown relative to the VSS. Also drove for months with a broken speedo cable and no codes were thrown. At one point the FJ60 speedo was consistently way off (don't remember if it was showing excessively high or low speeds) and no codes came up. With the FJ60 speedo needing replacement I swapped in the FJ62 unit.
 
ntsqd said:
I'm wondering if these could be used for the VSS in engine swaps as well. Any idea how many pulses per mile these produce?
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Maybe - it depends on the type of vss your new engine uses. Most likely, with minimal interface electronics. I plan on using the one in my FJ62 to drive the transmission TCM for the AW450 that is behind the Isuzu 4HE1 (when I can get back to that project)

The FJ62 produces 4 pulses per speedo cable revolution. IIRC, there is some defacto standard for how many revolutions of the speedo cable per mile. I don't know the number but google should help.
 
Spike Strip said:
That's interesting - I'll have to pull open one from a 60 and see if it's the same.
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I looked at a metric speedo that I assume came out of a FJ60 but it could have been a HJ or BJ also. It did not have the vss. The non-vss speedo had a 3-pin connector of which only two were used for lighting. The FJ62 speedo has a 4-pin connector, two for lighting and the other two for the vss.
 
...

Here's what's inside a 60 series speedo - You tell me if it looks like a VSS - But that round copper wheel is definitely wired into the harness, and not just for lights.

(maybe I should roll my speedo back a 100K miles :D)


:hhmm:
IMG_2855.webp
IMG_2859.webp
IMG_2857.webp
 
Spike Strip said:
...

Here's what's inside a 60 series speedo - You tell me if it looks like a VSS - But that round copper wheel is definitely wired into the harness, and not just for lights.

(maybe I should roll my speedo back a 100K miles :D)


:hhmm:
Click to expand...
If you have the 4-pin connector, the black & blue wires should connect to the reed switch which should be adjacent to the cup that is spun by the speedo cable, In the first photo, I've identified what I think may be the vss reed switch. I can't really tell from your photo. The 2nd photo is of a reed switch. This one came out of security system door sensor but you get the idea. The speedo switch may be different in size but generally they are a little glass tube with a set of contacts sealed inside with a wire coming out of each end of the tube.

An easy way to tell is to connect a continuity tester to the black and blue wires. As you rotate the speedo cable, you should see the tester switch from open to closed four times per revolution of the cable.
vss.webp
reed-switch.webp
 
Yeah, difficult to tell what's there, even with me looking at the speedo, but there does appear to be something like the reed switch you posted embedded in the board. Will do the continuity test you suggest tomorrow. I'm too tired at the moment to hunt for the multi-tester....
 
Ah, that probably wouldn't work w/o some electronics on the input end as well as possibly on the output end. As I recall most, but not all, ECU's/PCM's want to see 4000 pulses per mile. A normal VSS is inductive rather than being a switch. So there may need to be something on the input to step the voltage down to the normal inductive voltage (~1.0 volt?) in order for the switch to work. Then it may need to use one of the speedo correction boxes on the out put to get to the correct pulse count per mile.
 
Speedometer Calibration

On the face of the speedometer, just below the tripmeter reset knob, is the calibration standard for the speedometer. On my FJ62, it says 60MPH/1026 RPM. So for each mile traveled, the speedometer cable should turn 1026 revolutions x 4 pulses per revolution = 4104 pulses from the vss per mile traveled.
 
I'm assuming that if it wouldn't cause hard starting, it wouldn't cause a truck to not start at all then? Mine recently decided it wasn't going to start anymore and the only code it's throwing for the VSS.
 
On a vehicle of 62 vintage, the only codes it throws are emissions- related.

So it might not be getting spark, but the computer won't know about that...

Only with later (obd2) computers do you get full diagnostic capability...
such as it is.

t
 
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