RB25 Speed sensor wiring - HELP

[Iam99x]

Okay, I have studied every ECU pinout and wiring diagram that I found and still can't solve this issue.

I have a 1990 240sx with a RB25 S1 swap. Everything works as it should except the speedometer.

I am positive that the plug under the dash is wired properly, but their is still a problem.

Can someone tell me exactly where the wires go that come off of the speed sensor? One wire is Yellow/Blue, and the other is Yellow/Green. I am pretty sure that I am having a continuity problem somewhere, but I can't find where.

I'm am going to rewire the speed sensor to the ECU with primary wire, and then remove all of the unnecessary (old) wiring. My time to work on my car is limited due to school and work, which is the reason I would rather rewire than diagnose.

I am positive that my gauge cluster and speed sensor both work properly.

Thank you for any help.

[Cameron]

are you using 300zx speed sensor?

[Iam99x]

Nope. I'm using the OEM R33 one.

[Iam99x]

No one knows this?

2 wires off of speed sensor. Where do they go?!

VSS -> 2 wires -> Plug -> 2 wires -> Wiring harness -> ???

/sadface

[Iam99x]

^^^

[Carryl]

iirc the ecu gets its speed signal from the cluster.

Vss ---> 2 wires ----> cluster ---->ecu

[Iam99x]

iirc the ecu gets its speed signal from the cluster.

Vss ---> 2 wires ----> cluster ---->ecu

From what I've looked at it looks like they, or at least one wire, goes to the ECU first. Hell, I don't know.

Anyone?

This is a mystery that someone has got to know the answers to.

Tell you what, everyone always has this problem with wiring a RB25 to an S chassis car. When I figure all of it out, I will make diagrams, and maybe a video with detailed step by step procedures to do it right at no cost.

[Carryl]

i wired the rb25 cluster into my s14............the 2 wires from the vss go along the same harness with the oil pressure sender ....those 2 wires from the transmission go directly to the cluster...red wire and cant remember the other one off the top of my head........ and then from the cluster to the f3/f4 plug ... cant remember the colors not sure if they would be the same as your car as i have a jdm rhd s14

[Iam99x]

i wired the rb25 cluster into my s14............the 2 wires from the vss go along the same harness with the oil pressure sender ....those 2 wires from the transmission go directly to the cluster...red wire and cant remember the other one off the top of my head........ and then from the cluster to the f3/f4 plug ... cant remember the colors not sure if they would be the same as your car as i have a jdm rhd s14

I thought the wires from the VSS went to the ECU, then the cluster. So BOTH wires go to the cluster, then to the ECU?

If I understand that correctly, I may have a chance at getting this right.

Thank you very much.

[platez808]

I just did my vss wiring so i remember it pretty freshly.. and i'm going to assume that this is for a s13.. thats what i did mine in so thats how i can best explain and i dont know if its different in anything else..

but from the speed sensor there is the plug and this plug connects to the vss plug on the s13 lower harness. This plug is connected to two wires, Y/B and Y/L. . The Y/L and Y/B wires go through the lower trans harness to the plug by the engine bay fuse box. From there they goes to the speedometer where they transmit the signal. Then from the speedometer there is Y/G wire that sends the signal (not sure if its translated in anyway by the speedo but i'm guessing it is) through your dash interface plug to the ecu which should be spliced with the Y/G wire off of the RB25 ECU.

hope this helps.. good luck

Modified by platez808 at 1:43 PM 8/13/2009
Modified by platez808 at 1:44 PM 8/13/2009

[platez808]

sorry.. had to make a couple corrections to my earlier post

[Iam99x]

Can you spell out the wire colors, please?

Thank you for your reply.

[platez808]

No problem

Y/B= yellow/blackY/L=yellow/blueY/G=yellow/green

[Iam99x]

Awesome. Thanks. I'm at school, and about to go to see what I can do with this thing.

[Iam99x]

Okay. I've narrowed a few things down...

I have continuity from the VSS to the plug by the engine bay fuse box. From there, the wires change colors. The Yellow/Blue wire is now dark blue, and the Yellow/Black wire is now dark red.

Any idea where these wires go to next? IE: Another plug or straight to the gauge cluster.

Thank you guys for all of your help. I feel as if I'm getting somewhere now.


Modified by Iam99x at 9:40 PM 8/13/2009

[Iam99x]

The 2 wires that are closest to the camera are the ones that I am referring to.



This is the Yellow/Black wire that I have no idea where it's supposed to be.

[Iam99x]

Anyone?

[dg_performance]

Im working on a s-14 but it might be similar?? ...Im pretty sure your yellow/green from the rb speed sen ends up wiring into that dash plug (that looks like a mini ecu plug) the original location from rb to the ka plug are diff.... the Y/G wire should go to pinout 24 which is where the original ka signal wire would have went to. you might want to check that pin to see if you wired it correctly. The RB speed wire originally went to a diff pin location which would be wrong if you did not rewire it. Or you might have a broken wire there???If you have your old ka harness layin around look at that pin location and trace that wire to see if it went to the speed sens plug that you would have cut off and reused on the rb.

[Iam99x]

I think the plug you're talking about is in between the cluster and ECU.

[Iam99x]

LOL I think I've found my problem...



Eh?