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Old 05-14-2012, 11:45 PM   #1
kast1376
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Default Confirmation for speed sensor cable

I am installing a new stereo this weekend, and I need to tap the speed sensor wire for the GPS to work properly.

I just need a confirmation that it is the WH/OG wire, pin 68 on the PCM.

Now I have no clue where the PCM is, as I haven't dug into the car that much. Where is this located within the passenger compartment? Is there a closer spot to tap in relation to where the stereo would go?
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Old 05-15-2012, 07:19 AM   #2
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The bad news is that there is no Vehicle Speed Sensor on the GT's.

But the good news is that the PCM uses the transmission OSS (Output Shaft Speed) sensor and parameters programmed in the tune to create a VSS signal on pin 68 of the PCM.

More good news is that it can be tapped at the radio, as shown in the diagram below:



It is fed to the radio for the vehicle speed controlled volume setting.

I find it curious that the GPS should require a VSS signal, as a GPS is entirely capable of calculating speed all by itself--and far more accurately than the vehicle's system. With 4 or more channels locked in a GPS is accurate to 0.1 mph--maybe it's so the GPS can display something if it can only lock onto 1 or 2 satellites?
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Old 05-15-2012, 06:20 PM   #3
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Thank you for the help Cliffy!

The install instructions says it is for the GPS, but does not clarify. I would guess it is for the reasons you stated.

However, I am also guessing it is so the DVD player cannot be used while the car is moving. Grounding out the green brake wire was a common way to allow the DVD to play at any time, but newer models supposedly are tied into the speed sensor.
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Old 05-15-2012, 06:24 PM   #4
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Quote:
Originally Posted by kast1376 View Post
Thank you for the help Cliffy!

The install instructions says it is for the GPS, but does not clarify. I would guess it is for the reasons you stated.

However, I am also guessing it is so the DVD player cannot be used while the car is moving. Grounding out the green brake wire was a common way to allow the DVD to play at any time,
but newer models supposedly are tied into the speed sensor.
That makes more sense! I suspect if you leave it disconnected the GPS will be just fine...
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Old 05-15-2012, 09:20 PM   #5
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Quote:
Originally Posted by cliffyk View Post
That makes more sense! I suspect if you leave it disconnected the GPS will be just fine...
I plan to run it un-tapped and tapped and see if it makes any difference in the GPS, or if it just affects the DVD capability (if it does at all). Should make for a slightly fun nerdy project . It will be at least 3 weeks til I can get to it. Hope the Mach 460 holds on til then.
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