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Discussion Starter · #1 ·
I have a 90 d150 that I put the engine and transmission from a 99 ram 1500 into.  I am getting a code for p0500 "vehicle speed sensor a"  would that be the sensor on the transmission or the sensor for the rear end?  I still have the 90 rear end in and have plugged in the sensor into the harness but just have it tied up.  Will I need to swap the rear to get rid of the code?  Also I am wondering if I can tie into the speed sensor to make the speedo work, I have tried just splicing the wires in but that didn't work so I unhooked them.  Is there something else i need to make the 90 computer register speed?
 

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the rearend speed sensor is for the ABS only on the 1990

the rearend speed sensor on the 1999 is for the speedo and cruise control
 

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Discussion Starter · #5 ·
Ok that explains the speedo not working when I tied into the one on the trans then.  Looks like I need to find a rear out of a 99.  The sensor i just plugged in is out of an 01 2500 but it fit the plug, the speedo and cruise work in it it just has an abs light on so it must be different than 99.
 

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Your 1990 used a two wire “oc” vss which put out 4K pulses per mile. Your 1999 used a three wire “ac” halleffect which was 8k pulses per miles. Your 1999 Ecm will not recognize the “oc” signal. I ran into the same issue when doing my mag swap and I used a Dakota Digital SGI to convert the signal. It has two outputs, one for the speedo and one for the Ecm. Which trans are you running?
 

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In that case your 46re has two speed sensors, the forward one is turbine output speed and is used for governor pressure and the rearward one is for speedo. You need to use the rear one and covert the signal from sine to square wave so the speedo recognizes it.
 

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Discussion Starter · #10 ·
So that is the rear sensor with 2 wires on the back of the trans correct?  Will Dakota digital know what I need if I call?  I looked at the site but didn't see anything about dodges.
 

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If it’s the sensor from the 99 it will have three wires. As mentioned earlier in 99 they may have used the sensor from the rear end in which case you will have to get the dd sgi and play with it to figure out what signal it outputs.
 

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Dfeland said:
Your 1990 used a two wire "oc" vss which put out 4K pulses per mile. Your 1999 used a three wire "ac" halleffect which was 8k pulses per miles. Your 1999 Ecm will not recognize the "oc" signal. I ran into the same issue when doing my mag swap and I used a Dakota Digital SGI to convert the signal. It has two outputs, one for the speedo and one for the Ecm. Which trans are you running?
hey @Dfeland, when you did your swap, you simply reused the factory OC style VSS? I am in the process of swapping my '90 TBI engine out for a 1996 Magnum. My plan was to use the later-style 3-wire plug and harness, then run a later model VSS itself. I would then put a digital converter on the speedo lead.

Not to get off topic, but while I'm thinking about it, what did you do for a fuel pump? Maybe send me a PM when you get a chance... I'd love to pick your brain a bit.
 

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Discussion Starter · #13 ·
I guess I have the early one then because the sensor on the tailhousing only has 2 wires.  I'm hoping the rear end sensor will work.  Then I'm pretty much down to gauges and getting exhaust done.
 

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Using a 96-97 PCM eliminates the need for the rear axle speed sensor. Those years used the trans/transfer case speed sensor for speedo and shifting and cruise. only ABS use rear axle sensor. This is how i did my 84 w150 with 96 magnum drivetrain. speedo is happy and pcm is happy.

Edit: The 99 PCM gets is speed sensor signal from the ABS module. The ABS module gets its signal from the rear axle (2 wire). It might be possible to just splice the ABS module to PCM wire for VSS (white/orange) to the trans/transfer case sensor and make everything happy. the modules all communicate via CCD bus so it may or may not work. would be worth a try with only 1 splice required.

Edit #2: this wont work because you wont have a typical 3 wire speed sensor in the trans like an earlier model year. may be possible to add one in to your extension housing (or swap in an extension housing from earlier truck) but tailshaft would have to be able to accept speedo gear as well.
 
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