Technical Questions and Discussions

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VSS

Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=2514
Printed Date: 25 April 2025 at 8:45pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com

Topic: VSS

Posted By: orange
Subject: VSS
Date Posted: 15 June 2011 at 3:16pm

I still cant get the vss signal from sensor to speedo successfully. I have wired
my own converter circuit and used other peoples, used 2 different ecms, and
different proms too, and no luck, its driving me crazy, the vss when hooked
directly to the speedo works perfect but when it goes through the ecm the
speedo only reads maybe 10% so when going 40mph it says 4mph and so
on, i cant find any similar stories anywhere, so i dont know what to do.

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Orange 4.9

Replies:

Posted By: Romeo
Date Posted: 15 June 2011 at 3:32pm

Beyond the fact this would be awesome for pleading ignorence when speeding excessively (I thought I was doing 20MPH officer, not 200!), is it not possible to simply modulate the input signal to the ECM up 1000% so that when the ECM pulls it back to 10%, you're back at the original value?

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Never shift into reverse without a back-up plan.

Posted By: orange
Date Posted: 15 June 2011 at 3:53pm

Thats what i am ready to try yes, but thats not how it is supposed to be and i
dont know why it isnt working.

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Orange 4.9

Posted By: Romeo
Date Posted: 15 June 2011 at 4:38pm

Could be another sensors signal (Crankshaft Position Sensor/CKP, Camshaft Position Sensor/CMP, Ignition Module Base Timing, etc...) which would all look slower, especially in higher gears. Could also be that the ECU is used to seeing a signal ten times faster, and is thus designed to correct for it. Could be many more things as well. Not entirely sure, to be honest. Easiest solution would be to hook up a GPS, hit the highway and compare speed actual (GPS) to speed output (Speedometer). That will give you as precise a ratio as any, from which you can correct the cheap and easy method - namely, by altering the input signal.

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Never shift into reverse without a back-up plan.

Posted By: Dawg
Date Posted: 16 June 2011 at 12:13pm

You need to measure the Vss frequency and strength to see what is going on. Not something you can do with wrenches.

There are units you can buy to put the frequency where you want it. But you still need to know how to use test gear.

Dawg

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You dream it up....I'll make it