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Speed Sensor and Pulse generator

Old 11-06-2018, 10:18 PM
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Join Date: Aug 2017
Location: California
Posts: 3
Default Speed Sensor and Pulse generator

Going to try and lay out my issue as thorough as possible.

So I am using a 1989 Mustang 5.0 and AOD set up in a 1949 Ford F-1 resto mod. I am wiring the motor with Ron Francis 5.0 MAF harness . It comes with the Vehicle speed sensor connection, which from my understanding for the most part is for cruise control, tho Iíve read different scenarios where not using the VSS has the car running rough. Would prefer to keep it wired so I donít run into issues later. However tho, for my dash, I am keeping the same dash cluster configuration , except my speedo will be digital. This means I need to convert my speedo cable to a pulse generator.

Has anybody converted their speedometer to digital and found a way to both use a pulse generator and still occupy the VSS connector to the ECM? It seems like something someone would have done already, but I canít find anything in any forums or any parts/adapters.

does anybody know what signal is being sent to the ECM thru the VSS wiring? Is it possible to splice the VSS wiring back from the motor harness and tie it into the pulse generator wiring? I assume I would need to them have the ECM programmed - if the pulse signal being sent is, in fact, a correct signal for the ECM to read.

appreciate any help

Travis3Miller is offline  
Old 11-07-2018, 06:02 AM
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Join Date: Jul 2012
Location: ohio
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If you had used a T5 from 2000 V6 mustang it would have a magnetic speed sensor in it that reads a reluctor ring on the output shaft. But I think the 94-95 mustangs use a digital signal generated by the VSS but still uses a gear to spin it but no cable, just a magnetic pickup. You may be able to get the VSS for a 94-95 and swap it. Besides the cruise control, the VSS on a MAF car also contributes data to the computer to adjust engine rpm between gears, and when letting off the gas and coasting. There have been people experience stalling when coming to a stop, and also hanging RPMs when stopping.
dawson1112 is offline  
Old 11-07-2018, 09:45 AM
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Join Date: Aug 2017
Location: California
Posts: 3

Yeah, I had seen the more recent transmission set ups while rebuilding my AOD, definitely more advanced electronically. And that was the issue - I rebuilt the transmission myself, and the AOD seemed the easiest for me to rebuild especially for my first time opening up and tearing down a transmission case.

I just checked out the sensors in the SN95 like you suggested- and they are essentially the same thing that I have.

heres a pic that might help. The pulse generator has 2 wires and so does the VSS (if these are both sending pulse signals I feel like they could be spliced together to both send the same signal to the ECM and my digital speedo). Like mentioned , the VSS is important for ECM to collect data, so I am really hoping to not have to abandon the VSS. Iíve tried coupling these things every which way I can think of and it just doesnít work.
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Old 11-08-2018, 03:39 PM
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Join Date: Aug 2017
Location: California
Posts: 3

UPDATE and Resolution for anybody having similar issues on their 5.0 MAF or AOD set ups converting to digital speedo:

I contacted Dakota Digital to see if they had any products for me. They didnít answer my question that I posed in this original post ó but they DO offer a solution
this allows you to plug in your VSS and your new pulse generator into the same unit and sending the same exact signal. If you donít want to spend the 85 bucks tho...
this pretty much confirms that you that you can splice together your 5.0 wire harness for the VSS connector into your new pulse generator .

find the positive lead of your Pulse Generator and tie it into the positive lead of your VSS wiring (test pin 3 of your PCM) and tie the ground wire of your pulse generator into your negative wire of your VSS (test pin 6 of your PCM).

This will most likely result in needing a tune, now that your PCM will receive the same pulse as the generator creates.

hope someone finds this useful at some point !
Travis3Miller is offline  
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