rcm

Should the speedo work with just key on and turning sensor
gear with drill?Or does it need to be running?

scope103

It will work with just key on, engine off.

On this site I have opined that testing VSS1 was probably beyond what the ordinary mechanic would want to try. Since then I've discovered that a 4Runner manual actually gives the correct procedure to test it! http://www.ncttora.com/fsm/1990-1995...e/combinat.pdf (page BE-48)

It's still not trivial (hard to connect to the pins of the connector), but if you can test a TPS then you could probably test VSS1.

thook

If you're talking about the "non-cable" type speed sensor at the transfer case end, turning it by hand is sufficient, IIRC. And, yes, the key needs to be on so there's voltage to it. Conversely, you could jack up the rear end with the vehicle in N and spin the rear wheels or driveshaft.

What exactly are trying to accomplish, anyway?

Edit: Ah, scope......ya beat me to it.

rcm

Well my original sensor finally quit do to one pin corroded and broke.Bought from salvage yard and it worked about three months.So i bought another thru parts store .when i pulled old one out the plastic gear was stripped.so i had an extra gear,put it in the new one and still didnt work.So i pulled it and the gear was stripped.Pulled back cover on transfer,the worm gear had some smushed places on the teeth,small one on the oil gear,little play in the bearing.So i have ordered the new parts from toyota east,but thought i would check both sensors again and neither work with the key on turning it will a drill.So i do have 12 volts going in.Does the sensor need to be grounded to case?

thook

Sorry, dude......I can't honestly answer that. I forget how the VSS is electrically routed to recommend how to troubleshoot. I'd have to look it up. Hopefully, Scope can answer before that happens.

rcm

ok i looked at diagram.Tested the old sensor.hooked to battery positive,ground and checked output.It will show around 12 volts,turn gear by hand and drops to 0 volts,turn again back to 12 and then to 0.The new one will show around 12 volts,turn gear drops to 11 or so ,turn again back to 12.So according to diagram the old one works right and the new is no good?

thook

Check that voltage changes from approx. 0 V to 11 V or more
between terminals 3 and 2.

It's says "approx." between 0 and 11, but because you're getting 12v at the high end, I don't think that will make any difference. On the other hand, the FSM states the voltage should change 4 times for every one complete revolution of the shaft. Does either sensor do that?

rcm

The old one does the new one doesnt.The new one is made in tawain....The old one really is just over 11 volts on the high side and 0 on the low.

scope103

No way to know for sure, but I doubt that 11v will pass for "approx 0v." IF you've got your test hook-up correct, the "new" one is probably not working.

That said, a few years ago I tested mine, not by testing the sensor directly, but by testing the speedometer from the sensor connector. I used a digital signal generator. I was able to make the speedometer move (to any speed I wanted), which told me the sensor was no-good. If you had the same setup you could adjust the signal amplitude (and base line) to see if switching between 12v and 11v would be enough. But even as I type this it sounds like too much work.

thook

It doesn't sound like the new one is working right. Atleast, not according to the way technical illustrations show how the VSS internals and the generated signal works. The illustration shows a line (the signal) in a wave pattern moving back and forth between 0 and 12v's. A VSS moving only between 11 and 12v's doesn't really jive with that. Plus, you said the new one doesn't change 4 times every revolution, right?

What I was referring to earlier, some Toyotas were equipped with a VSS that sent it's signal first to the dash meter and then to the ECU. Others send the signal first to the ECU. I believe the style used in ours is the former.....as Scope's experiment seems to show. Seems to me if your old VSS is producing a signal according the FSM testing procedure and is still not affecting the speedo, something may be awry with the dash meter or wiring to it.

However! Something occurred to me as I writing all this. You know how the speedo really won't register until the vehicle is moving fast enough? Well, I believe what I said earlier may be entirely wrong. Turning the VSS by hand may not actually be enough to register on the speedo, though it's obviously enough to test it. You probably need to use the drill so a signal is generated fast enough to register on the speedo.

Sega

Where is the V's located? Any pics would be greatly appreciated.