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Old 11-16-2007, 12:01 PM   #1
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Default Where can I get the speed pulse off the ecu?

I installed an AVIC N2 nav system in my car and it has a plug for the speed pulse signal of the ECU. The manual for it says that it increases accuracy of the navigation because it sees how far the car has traveled. Personally I dont understand why it would need it seeing as how GPS can calculate my speed much better.

So, do you guys think I should hook it up and if so which line on the ECU is speed pulse?

edit: I modified the unit so it lets me watch dvds and use its function while the car is in motion but that is without the speedpulse wire, I also need to find out if adding it will disable the effects of that workaround.
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Old 11-16-2007, 12:24 PM   #2
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Thanks for letting us know what year car you have!
1.6 VSS can be found at the back of the instrument cluster. you have to remove the dash and solder a wire on. don't know about 1.8. may also be able to tap into an abs sensor if equipped. worst case scenario is you add an optical sensor to the driveshaft.

gps is not good for monitoring changing speed over short intervals.
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Old 11-16-2007, 12:45 PM   #3
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Quote:
Originally Posted by Ben View Post
Thanks for letting us know what year car you have!
1.6 VSS can be found at the back of the instrument cluster. you have to remove the dash and solder a wire on. don't know about 1.8. may also be able to tap into an abs sensor if equipped. worst case scenario is you add an optical sensor to the driveshaft.

gps is not good for monitoring changing speed over short intervals.
97 miata

edit:
http://mazda-speed.com/faq/audio/

Supposedly on pin H at the audio harness but thats if it were used as the main harness and not for headrest speakers which I had because my car came with the MPSS.

edit 2:
http://www.innovatemotorsports.com/r...azda_Miata.php

Shows pin 1M at the ecu.
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Old 11-16-2007, 12:51 PM   #4
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2F, green/red.
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Old 11-16-2007, 12:53 PM   #5
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How is your navigation system going to interpret the pulses from the ECU? Is this something you can configure? I somehow doubt that the nav system is going to speak Miata ... unless of course this is a standard thing.
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Old 11-16-2007, 02:21 PM   #6
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On NAs without cruise control or other VSS-dependent options, the VSS wire from the instrument panel plug to the main harness connector is sometimes absent, even though the VSS wire is present from the main harness to the ECU.

Pull the instrument panel and look at the back of it. Connector position 2F- you got a green/red wire there? That's it. If not, trace that line back to the screw on the back of the speedo that it goes to, and attach at that point.
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Old 11-16-2007, 02:25 PM   #7
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Quote:
Originally Posted by Braineack View Post
2F, green/red.
Quote:
Originally Posted by Joe Perez View Post
Connector position 2F- you got a green/red wire there? That's it.
My car has cruise control. So is 2F just the tach signal? Im looking at the harness in the MS howto.

So I can get it at two different places?

Id rather get it at the ECU then at the speedo because its just so much simpler to tap at the ecu.

Last edited by Saml01; 11-16-2007 at 02:39 PM.
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Old 11-17-2007, 02:43 AM   #8
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Quote:
Originally Posted by Saml01 View Post
My car has cruise control. So is 2F just the tach signal? Im looking at the harness in the MS howto.
No, it is not the tach signal. It is a signal which is driven off the speedometer and related directly to vehicle speed, not engine speed. Specifically, it is a reed switch placed inside the speedometer which provides a pulsed connection to ground, as a magnetic ring rotates beside it causing the reed contacts to alternately open and close.

Quote:
So I can get it at two different places?
You can get it directly at the instrument cluster, the cruise computer, the inter-harness connector below the steering column, the back of the radio, or any number of other places.
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Old 11-17-2007, 04:26 PM   #9
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Alright so I just gotta find the red/green somewhere that Braineak mentioned and im good.

I am guessing ill try to source it at the radio since that will make wire routing simplest.

Thanks guys.
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Old 11-17-2007, 04:51 PM   #10
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Quote:
Originally Posted by Saml01 View Post
I am guessing ill try to source it at the radio since that will make wire routing simplest.
On vehicles with the premium audio system, it is at pin 1H on the radio.
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Old 11-17-2007, 10:18 PM   #11
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Quote:
Originally Posted by Joe Perez View Post
On vehicles with the premium audio system, it is at pin 1H on the radio.
Your the man. Thanks again.
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