vehicle speed sensor question - 1992 NA EJ22

ysrebob · Post by **ysrebob** » Wed Mar 30, 2005 9:59 pm

hello,
Anybody know WHAT VOLTAGE the ECU puts on the vehicle speed sensor in a 1992 Legacy? 5v? 12v? My understanding is the computer applies a voltage to the speed sensor and expects to see a pulsed ground, 4 pulses per wheel revolution... correct me if I'm wrong though.
thanks much,
Robert Harris
92 Legacy EJ22 NA
"ysrebob"

Post by **Legacy777** » Fri Apr 01, 2005 5:26 am

It's a pulsed output from the speed sensor to the ECU. I think it's 5v, however I'd have to double check.

vrg3 · Post by **vrg3** » Tue Apr 05, 2005 6:56 pm

Yes, it's 5 volts. The ECU contains a pull-up resistor that pulls the line to the 5v rail. The sensor itself pulls the signal to ground.

I don't know if the 4 pulses per wheel revolution part is correct or not.

ysrebob · Post by **ysrebob** » Wed Apr 06, 2005 5:38 pm

Thanks for the help guys! I have had such good experiences owning Subarus that I use a 92 EJ22 motor in my VW camper (not a rare conversion). Seems the Subie engine computer wants to see some kind of VSS signal or it stalls after any kind of engine braking though... thus the question... I had jury-rigged a speed sensor but it died -- burned transistor I think; just made a new one one designed for 5v and all is well again! These 2.2L Subie motors rule!!
Robert
<http://www.people.cornell.edu/pages/rdh ... ex_vw.html>

vrg3 · Post by **vrg3** » Wed Apr 06, 2005 6:34 pm

Woah, are you here in Ithaca, Robert? On campus perhaps?

Why do you need to design a VSS for 5v? After all, it's just pulling to ground, right?

Couldn't you just epoxy some magnets to the driveshaft and mount a reed switch near them?

Depending on how your cooling system is set up, you might need to make sure the VSS signal is somewhat accurate; in stock Legacy form it's used in radiator fan control.

ysrebob · Post by **ysrebob** » Fri Apr 08, 2005 3:52 am

hiya vgr3,
Yeah, I'm a grad student here (biologist). Small world, hey?!! Goes to show how much Ithaca is a Subaru town. Reed switch would work great but it seemed like time to failure could be an issue going through so many cycles per mile... though maybe this is how the stock Legacy VSS is done? Went with a solid state optical setup instead. Pmail me if you get a chance... would love to talk but don't want to drag the forum off topic. rdh24@youknowwhere
best,
Robert

isotopeman · Post by **isotopeman** » Sat Apr 09, 2005 4:57 pm

So would this work for our Subarus that have the speedo-cable attachment in the transmission broken? I was considering putting a magnet on the driveshaft for a bicycle speedo just to know speed and distance. Cruise control would be nice. I'm sure somebody else has noticed how the drive pedal's location at that hump in the floorboard leaves you with an angled foot. This is quite uncomfortable after awhile.

gnuman · Post by **gnuman** » Fri Apr 15, 2005 4:54 pm

OK, I have a 92 with a 5MT and my speedo generally reads about 10MPH high. would replacing the VSS behind the dash fix this? Is there annother VSS in the 5MT where the cable goes in, or is this a one sensor application? I know the 4EAT has two sensors: one in the tranny, and one behind the speedo. I'm wondering about the 5MT. If replacement is the best bet, what is the name of the part? VSS2?

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vehicle speed sensor question - 1992 NA EJ22

vehicle speed sensor question - 1992 NA EJ22