speed sensor connection

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speed sensor connection

Postby gt304 » Wed Oct 01, 2008 7:57 pm

hi
friend has vr 5.0l auto and converted it to manual t56 using standard auto computer, used a converter box from pcm to dash to correct speedo and speedo working fine. Got car tuned and getting good power but at low revs it bunny hops and gear box jerking noises. i think computer isnt reading speed correctly any advice on correction it. Thanks
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Postby GTS215i » Wed Oct 01, 2008 9:58 pm

converter box from pcm to dash

Thought the converter box was installed between sensor & computer - atleast thats how i wired mine ! Car not going yet though....
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Postby DerekBell » Wed Oct 01, 2008 10:04 pm

Not 100% sure, but I think this model uses the PCM to send the signal to the dash. If you haven't made the appropriate changes to the calibration to tell it the speed signal is different there will be a problem.
I beleive it was the earlier models that sent the speed signal to the dash first.

I would recommend putting the correction box between the PCM and the speedo, hence correcting the signal into the PCM as well.
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Postby PVE » Wed Oct 01, 2008 11:29 pm

Check out your PCM input/output terminals list... this will indicate if the speed sensor goes to the PCM and if there is an output to the speedo.
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Postby gt304 » Mon Oct 06, 2008 5:21 pm

from my understanding the signal from the t56 sensor is different but is still giving a reading to the computer(pcm), but because its not correct, the computer has drivability problems which dont exist under max power. By saying that my previous car was a vs man t5 5.0l which had a ecm and had simular issues with drivability in lower rev range which was tuned without a converter box which later i installed one and i was amazed at the difference not power but smoothness and not bunny hoping at low speeds.
Basically i think his computer hasn't been conpensated for the diff gears when tuned so can anyone tell me that by putting a converter box from speed sensor of t56 to pcm will speedo be corrected also or will that not work (maybe due to different signal which box is out of gen 3) hope havent confused anybody. thanks
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Postby DerekBell » Mon Oct 06, 2008 5:38 pm

Just checked my VR wiring diags I have here (forgot I had them). The speed signal is split from the sensor to the ECM, and the speedo in manual, it goes to the PCM first and then to the speedo in auto.

You will need to put the converter box before the split to ensure the ECM and the speedo are getting the same signal. The Converter will need to go in the Purple/White wire straight after the speedo connector (i.e. remove the wire from the connector, put the converter input straight into the speedo sensor, and the output into the wire you took out of the connector).

If doing this you get your speedo reading correctly, the signal to the ECM should also then be correct.

Hope this helps

Derek
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