Prep Your RB Lower Harness here!

[Slo_240sx]

I thought it would be a good idea that while I had my motor on the ground I would do a write up of what needs to be done to the KA lower harness to make it fit onto the RB.

Jonpowell is a firm believer in this and you can duke it out with him if you think you should use the RB harness.

Series II RB25DET S13, all S13s should be the same. Do this at your own risk!!! I will not be responsible for your mistakes and this is based on my knowledge and experience with my RB.

WARNING: do this at your own risk!! i am not responsible for *Jack* bla bla, you know how it goes. Now this guide is only for those that know basic engine wiring, have some clue so far on what is going one but just need to know the specifics to get it started. Thanks OpenSource...

Also included I will should you how to properly splice wires. Don't use gay splice/butt connectors they will only cause you pain in the long run and I will flame you. Spend the time and a little bit for materials and I promise all will go well and you will be glad you listened to me!

Now on with the show...

Prepping that Lower KA harness for your RB

1) Take off both harnesses from the KA and your RB motor

2) From your RB Harness cut off the Oil Pressure sending unit plug, it has two wires - YLW/WHT and B and it is located right next to the oil filter.

Now You are going to want to cut atleast this much off because it has to be slightly extended.

The Yellow with white wire is for the oil light and the blue wire is for the oil gauge. The stock Ka cluster doesn't have a oil gauge so the blue wire won't be used. If you are using the RB gauge cluster than you want to be using this blue wire and are going to have to hard wire it to the cluster. If you are using the stock cluster than cut the blue wire, or leave a pig tail on it if you plan to use a oil pressure gauge because thats what its going to be hooked up to.

2 Wire RB Oil Pressure sending unit plug

1 Wire Ka Oil Pressure sending unit plug

Now here is how to PROPERLY splice wires:

Cut off about half an ince of insulation throw shrink wrap on and fan the wires out. Alot of people use adhesive shrink tubing for insulation to keep moisture out of your connection. It is HIGHLY recommended. You'll forget to put shrink wrap on a couple of times until you get used to it ;-)

Now intertwine the fans and close them like so:

Now twist the wires opposit of each other. 1 clockwise the other counter clockwise. When that is done it should look like this:

Now *Solder* it in place don't go over board with it, lightly cover it and it WILL hold. Once again adhesive shrink tube helps. LET IT COOL DOWN! If you pull the shrink wrap over it you know what happens... you get to do it over. Let it cool then pull the shrink wrap over and heat that sucker up so it tightens.... don't burn it.

End Product: Its Perfect!

3) The output wire from the alternator on the KA has a slightly smaller hole to fit over the stud of the RB harness. Ream out the hole from the KA harness to the RB alternator. I just used a dremel.

Rb compared to KA

here it is reamed:

4) From your Rb harness unravel the looming and take out the knock sensor harness. The main plug is at the front of the intake. its the Lower Plug of the 2. I made my harness pretty - loomed and taped it. I suggest you do the same because its more protection than anything else.

Lower plug for Knock sensors

Here what is should look like unravled and separated:

5) With the main plug in bring the harness back and plug in the 2 knock sensors and the one sensor hiding under the intake.

Tape it in place and you are set for that part of the harness.

6) Run The wires back off the lower harness to the back of the transmission and all of these should plug right in except for the Vehicle speed sensor.

You are going to have to use the RB25DET speed sensor with the Rb25DET trans. The RB20 is the same as the KA but they differ from the 25. The 25 is about 2 inches longer than the KA speed sensor so it won't work.

Plus, the KA speed sensor has a long harness attached to it with the plug located at the back of the motor while the 25 SS is a short plug having the RB harness run to the back of the motor.

Here is the RB compared to the KA:

You can obviously tell the difference. Resort? extend the KA plug all the way back. The VSS plugs are both the same. Instead of using the KA plug I unwrapped the RB plug and cut the pig tail to the length I needed so I didn't have to make 4 splices instead of two. Use that brain of yours!

Heres the plug that won't reach for the VSS:

And here is the RB VSS in the transmission:

Now this is up to you. The Starter solenoid connection from the KA to the RB doesn't quite fit on the spade connector right. You can swap you RB plug onto it or leave your stock KA on it. It will fall off eventually and may even become a bigger problem later on. My suggestion is change it over.

Heres what that plug looks like Rb compared to KA:

7) Plug everything in - Alternator, Starter, speed sensor, other misc trans sensors, knock sensor harness, oil pressure sending unit etc.

8)Tape and zip tie it all in place and make sure your connections are good.

You are all done wasn't that easy!?

FREAKING DONEReverse lights workSpeedo worksAlternator worksStarter worksDONE!

This is SOOOO Easy that there is no extra step for a beer break!

Please post if you want to comment or see any mistakes, i'm not perfect!-Alex
Modified by Slo_240sx at 8:59 PM 2/21/2005

[kouki-gymkhana]

OMG, you are my hero! Thanks so much for the step by step guide! I haven't done the swap yet but I'm sure if there are any errors the others will chime in and set things straight.

-kouki

[NISMO_RB25]

yea i got to say that is one of the best writeups i have seen so far. The lower harness isn't complex, but lots of people have questions about it, and it is great to have this on here now.

Good job!

[yellow_jacket]

Great write up!

[Slo_240sx]

Thanks guys! feels great to finally contribute to Nico. I figured since everything else has been written up about then I might as well do this since there are alot of questions. Thanks Nismo for the help about the VSS. -Alex

[Bluefire]

Also, if you want to be anal like me you can swap the starter solenoid plug from the RB harness to the KA harness. The KA plug doesn't securely clip on and can tend to fall off sometimes

-Bluefire

[Slo_240sx]

LOL I had that but decided not to put it in Lmao. Its going in now though now that you mentioned it. I got lazy and didn't bother.-Alex
Modified by Slo_240sx at 5:19 AM 2/19/2005

[OKCA18DET]

nice...now someone needs to do the exact same for the rb20 so i can have visuals i know people say its the same but just for comfort hehe

[Carl H]

you silly rb25 guys and knock sensors that are on the lower harness and vvl that sometimes works. ;P

[Slo_240sx]

hehe.... you guys are going to have to bare with me. My pic server sux and they said when I was done my daily limit was eceeded. Should work in a day.

[JonPowell]

I bet TONS of people will still try the KA and cry when nothing works though.

GREAT JOB!

Hopefully everyone will take heed and follow your great advice. That way they can stop crying.

I say from here on out, anyone using the KA harness deserves to live in limbo when they have problems. There is NO excuse for it anymore.

Who else says sticky?

[dekand]

My only correction is that you spelled solder wrong...

[FrostyRB]

One thing I would like to add is use the shrink tubing with the adhesive in it. It will not let any moisture get to your connection. Good write up that is the exact same way I did mine, but with the adhesive shrink tube.

[Slo_240sx]

All corrections have been made or added. Thanks for the input guys. I'd love it if this became a sticky I just need a better web host. If you can't figure out how to wire this up with this write up you don't deserve to be working on cars period. This is basically idiot proof. Once again thanks to the guys at nico club for all the help,its great to contribute back!

[NISMO_RB25]

you can post your pics in the members ride section and link to there. that way they are already one the nico server

[gawdzilla]

good post, very easy to follow. Easier to follow than the ones which just say something like "plug red/blue wire into green/white wire on grey plug" you actually mentioned what the wires do!

[BoostFab]

nice write up...i vote for this to be stickie

[Slo_240sx]

Thanks guys i'd love it if this got stickied. Some many people ask about the lower harness whether it be about the VSS, knock sensors, alt etc... If they follow this its ALL done. I just got out of a thread where a guy had no idea what he was talking about when he mentioned the VSS. Thats why I included pix....

[Slo_240sx]

Anyone else say sticky?

[NightKids2]

I think it should be.

[NISMO_RB25]

i vote sticky. if you can't get it sticky then maybe it can get added to one of the other stickies.

[JonPowell]

Why not email it in a word format and I will post it on my Yahoo group. Then its sticky for sure!

[email protected]

[Slo_240sx]

Will do, I'm gonna upload my picture into my members rides that way the url will never change and you can keep the pics on as long as nico is up. I have to go to work though I'll email you later tonight. Thanks jon-Alex

[240sxed]

Dude, I never saw this but i was searching for if a z32 intake maf adaptor will fit on the rb25 stock one and found this thread. GREAT WRITE UP ! It just confirmed all the basics that I needed to know. I've done this similarly on a SR swap, and glad to know it still works. Can you rehost/fix the pictures? if you need webspace i'd be happy to provide it free unlimited as far as picture space.

[Slo_240sx]

Yeah I can reupload pics but I'm gonna need that of yours if you want them back up. Anyone say Sticky again?

[240sxed]

sure, just go to http://www.speeddreamz.net, register and post in the user's gallery

[JonPowell]

I have this whole thing in word format, with pics, on my Yahoo group in the files section.

[Valley]

i say stuck.

as your group requires one to join it.
Modified by Valley at 10:07 PM 5/20/2005