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Speed Sensor Wiring

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I was hoping to get a little help, or at least a good start on my issue.

I purchased an S15 Spec S that was converted with an S14 SR20DET and tranny. I call her my Spec R/S (or S/R, not sure which way I like it better). I'll be posting a build thread once I get off my lazy @$$ and transfer my pics off my camera.

With that said, the speedo has never worked. The guy I purchased the car from, bought the car from his friend while in Okinawa. His friend was the one that got it converted, and doesn't actually know the full history of the car. I've done quite a few mods to the car already, but my next goal is to get the speedo working.

I know the S15 has speed sensors in the rear diff and ABS sensors in the front HUBs and the S14 has the sensor in the tranny. I haven't gone underneath the tranny to see if the sensor is in there (I don't even know where to look atm), but I do believe the sensor in the diff is connected.

Now what are my options with getting the speedo to work? Would I just try and connect the speed sensor from the tranny to the ECU (I have a Power FC D-jetro), or would I go off the rear diff and ABS? Or would I try and wire them all in together?

Anyone that has any experience with this mod, please chime in with any tips and tricks you may have.
 
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Hi mate

Ive got a similar prob, ive ordered a dekota signal converter. Soon as it come ill be having a play to get it to work so will update on progress. Gonna take another week or two to come.
 
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I'm not looking to purchase any type of converter. I know it can be done with an S14 motor, but since I wasn't part of the process of putting it in, I'm not sure why they didn't do it in the first place. I'm hoping to find out which sensors people have used to get the speedo to work.
 
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The reason i need a converter is the signal from the gearbox uses a different frequency to what the speedo accepts thats why im using the converter to get the signal from the ecu to the speedo.

Not sure if youve got the exact same prob as me but thats what im doing to get around the issue.
 
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I'll be following your thread. To my knowledge, I still have my ABS installed, so I'm hoping I can just keep that setup, but if not, I may need to get myself a converter.

Where did you pick yours up from, and how much was it?
 

adzsy

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You need to connect two wires from the old Auto control box connectors (near the now clutch pedal). Try plugging the automatic Control module in and see if the speedo starts to work thats what I did. If you struggle I'll go out and see which wire I shorted.
 
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So last night I decided to take a look in the dash to see if there was anything that looked out of the ordinary. Of course everything seemed out of the ordinary since I don't have much experience with wiring, lol. There was a ground wire that was grounded, but but wasn't connected to anything. I took the cluster out and discovered that the ABS light was connected to the oil light. It was done this way to pass an MOT. So I was mistaken in thinking that the ABS was working properly.

I'm now thinking that the ABS is what is causing the speedo to not work properly. I've checked the ABS ecu and as far as I can tell it's hooked up properly. The fuses were all good and I checked the ABS sensor in the rear diff. I'm not too happy with how the wiring looks on the ABS sensor, so I plan on splicing into it and cleaning it up. I know there are 2 other ABS sensors in the front wheel wells which I'll take a look at when I get some time. I did a quick look over of them and traced the wiring back through the engine bay and they looked ok. I'm not sure what else to check for the ABS.

I'm going over the texts that I received from the previous owner and he mentions that he recalls the diff not being hooked up. Is it even possible to not have the rear diff connected? If so, how would I reconnect it?
 

adzsy

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I have just done an RB25 conversion to my spec S so knowthis quite well.
On the spec S the ECU takes the speed reading from the vehicle speed sensor(VSS) in the gear box. It connects through one of the connectors on the insidesuspension turret near the fuse box. You should be able to connect the VSS fromthe S14 box to this. I have connected the VSS from the RB gearbox and have itall working (other than its in KMH).

This is the route it would take to help it make sense;

Starts from the VSS in the gearbox.

Via the connector from the gearbox loom to the main harness (inside the strut)

It then feeds into the Automatic control module - You will no longer have thisconnected, so need to short two of the wires (some people leave it connectedjust for the speedo)

From here the wire splits somewhere in the dash and it feeds the ECU and thegauge cluster.

The best thing to do is get the S15 workshop manual out and really understand what’shappening.

Somebody may have tried to connect the speedo to the ABS sensor so don't ruleit out.

Does your ABS physically work?

 
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So the Spec S gets it's speed reading from the transmission like the S14. Then why does it have a speed sensor in the rear diff and in the front hubs? Or are these sensors just used for the ABS?

If it is from the tranny, then it seems I may be able to solve half of my issues. The next issue is why does the ABS light stay lit?
 

adzsy

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Yes they are just for the ABS. Thats not to say that someone hasn't tried to use it though.
 
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I don't think anyone has tried to get it working in the past. From what I have been told, the guy I purchased the car from bought the car with the motor and tranny swap already done from a friend of his. His friend was the one that got all the work done to it. The previous owner did say something about them not trying to get the speedo working because the wiring was too short. I have no idea what wiring he is talking about, nor does he know, but maybe it has something to do with the wiring from the speed sensor is not long enough to reach wherever it needs to go.

I'll have to get it up on a lift to see if there is even one connected. Are you able to take a picture of how you have it set up? I took a look at the wiring by the fuse box and I only found a ground wire that was grounded, but not connected to anything. Not sure if has anything to do with the speedo or ABS. I have no idea on what to look for to see if they tried to connect the ABS and speed sensors together. I guess I'll start with trying to get the sensor in the tranny working first.
 

adzsy

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I am planning on MOT'ing it next week so whilst I am fiddling I will take some pics for you. All the engine loom was documented, but by the time I got the speedo I stopped caring and just wanted it done! I new I should have made some notes.
 
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Thanks, I appreciate it. I probably wont be tackling this job until the summer, but would like to know more about what I can do to help make it easier.
 
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