The RB20 Wiring Thread

Post by **Jamison** » Mon Sep 01, 2003 9:47 pm

Hi. I have been trying to gather info on wiring my rb20 harness up and I cant seem to find much info on it. I did a search and found one thread but it didnt go into depth.

I was wondering if anyone out there has a complete wiring write up on the whole process for an s13? To be honest with you guys I have no idea where to even start, which harness's to use, where to splice, what color wires to splice, do this while the engine is in or out, nothing.

If anyone out there can please post a complete write up (with pics if possible) then you have no idea how greatly I would appretiate this. Oh yea, I named the thread this for future referance if anyone else needs this info.

Thanks alot in advance for eveyones help.

Post by **spec-v5150** » Mon Sep 01, 2003 9:47 pm

I usually dont say this BUT SEARCH!!!!!! I know for a fact I JUST posted that wiring info up not too long ago. Maybe a month. It is here.

Post by **spec-v5150** » Mon Sep 01, 2003 9:47 pm

Okay dont search. I am having a hard tiem finding it. LUCKILY I had saved it on my PC at work......ENJOY

WIRING UP YOUR RB20 IN A 89-90 240SX - BY BRANDEN ROSAThis how-to is for 89-90 240SXs that came equipped with SOHC engines. Wiring up a 91-94 DOHC engine should be very similar, but not quite the same. This how-to also assumes that you already have the engine and transmission installed. If you are performing this swap, make sure you have the engine and transmission installed properly. If you have any questions, feel free to contact Branden (Nismo241) at [email protected]

1) Run the ECU harness into the passenger side of the car, extending the mass air flow sensor, and O2 sensor wires.

2) Locate 2 plugs on the RB20 motor harness. Both being rectangle and one having 6 wires, and the other having 8 wires.

3) After locating these, find the female end of each of these plugs and cut them back about 6-8 inches.

4) Locate 2 oval plugs on the KA chassis harness, one being grey, and the other being brown.

5) After finding these, cut the Black/red wire, and connect it to the Black/red wire on the RB plug that was just cut.

6) On that same plug, cut the Red wire and splice it to the white/black wire on the same RB plug.

7) Going towards the fuse box, there will be a white wire that goes into the box. Cut and strip both ends of it.

8) Splice the white/purple wire from the RB plug into the white wire.

9) Off of the ECU there is a Black/pink wire for the fuel pump, run a wire from the ECU into the engine bay to the black/pink wire from the fuse box.

10) Now there will be a plug with 2 wires in it on the KA chassis harness, one being white and the other being black/yellow. Find the black/white wire on the other RB plug and connect the two.

11) Coming out of the fuse box there will be a plug that contains a small white/red wire. Take that and connect it to the white red wire coming from the RB motor harness by the alternator.

12) Take the thick white/blue wire and run a wire from there to the positive battery terminal; that will charge the battery from the alternator. The way I did mine was I took the RB battery harness and connected it to the battery as well as the KA battery harness, that way it powers the KA harness and the RB harness, same goes for the negative battery cable.

Also........take the number 7 ECU wire (yellow/red tachometer wire) and splice it to the cluster plug that the tach goes into. I forget what color wire I spliced it to (maybe someone can interject...I REFUSE to rip my dqash off again to find out the color...LOL). This will get your tach to get a signal. I think you can just replace the KA tach with an RB tach if you got a cluster. I used an aftermarket tach. But you still have to plug the ECU to teh cluster plug. The SOHC wont work at all and the DOHC reads twice as high

Post by **Jamison** » Mon Sep 01, 2003 9:47 pm

thank you so much spec-v5150!!! I needed this so much. I have only one more question when you start I understand that you have the rb harness on the engine, did you keep the ka harness plugged into the fuse box under the hood of the car?

Oh yea for the speed sensor, I just replaced the mechanical one with my eletrical one and it plugged in fine. Is this what you guys do?

Once again thanks alot for this info!

Post by **Project240** » Mon Sep 01, 2003 9:47 pm

Exactly how different would it be wiring up a 91-94 DOHC with the same motor? Would this guide pretty much get me through it without too much trouble?

Thanks for the info, it may end up helping me as well whenever I finally make up my mind about what's going in the damn car...

Post by **blk90s13** » Mon Sep 01, 2003 9:47 pm

i am kind stuck at number 7 right now where u say the white wire going into the fuse boxx

i have three of them so wut the hell

now will a SR tach work ? or does it have to be the RB tach ?

Post by **Andrew85cm** » Mon Sep 01, 2003 9:47 pm

You could really use any of them i believe but if you look at the fuse box cover it says which is the ignition fuse and use the white wire that goes to that one. I am having a problem with my damn tach and temp... I can't get either to work and to the best of my knowledge they are wired correctly. So I am stuck.~ANDREW~

Post by **PROJECTRB240SX** » Mon Sep 01, 2003 9:47 pm

TACH IS PIN 7 ON THE ECU AND ITS A YELLOW/RED STRIPED WIRE IIRC.

THE WATER TEMP WIRE IS THE ONE THAT COMES OFF OF THE BLADED SENSOR IN THE WATER OUTLET. I CAN'T REMEMBER THE EXACT COLOR BUT I THINK IT IS EITHER A BLUE OR BROWN WIRE.

I'M SORRY I CAN'T BE MORE SPECIFIC BUT ITS BEEN A YEAR SINCE WE WIRED UP MY CAR.

Post by **Carl H** » Mon Sep 01, 2003 9:47 pm

the stock dohc tach will work, BUT it will read 50% higher due to 2 more cylinders.best bet is to swap in the rb tach, or if you dont have that get a recalibrated tach from ls auto.as for tach and temp, on the rb efi harness near the ecu plug there will be a white plug with a yellow/red and blue/black wire on it.wire these into the corresponding wires on the connector that the ka efi harness unplugs from near the glove box.also run a ground wire from the ka glovebox connector deal to the ground wire on the rb efi harness (its on one of the other white plugs) and you tach and temp should read.

Post by **Carl H** » Mon Sep 01, 2003 9:47 pm

also i did do a wiring writeup for putting an rb20 (any year) into an s13 (any year).i also did a simmilar guide for wiring the dash cluster to work for a 91-93 car and later year rb20 (no 'rb 20' embossed on the timing belt cover) cluster.

Post by **PROJECTRB240SX** » Mon Sep 01, 2003 9:47 pm

ACTUALLY THE RB20DET'S THAT WERE IN THE GTS-4 MODEL R32S DIDN'T HAVE THE RB20 STAMPED ON THE TIMING COVER.

Post by **PROJECTRB240SX** » Mon Sep 01, 2003 9:47 pm

WELL ATLEAST EVERYONE THAT I HAVE SEEN PICTURES OF.

Post by **sileighty89** » Mon Sep 01, 2003 9:47 pm

the water temp wire is blue/black

Post by **blk90s13** » Mon Sep 01, 2003 9:47 pm

10) Now there will be a plug with 2 wires in it on the KA chassis harness, one being white and the other being black/yellow. Find the black/white wire on the other RB plug and connect the two.

can someone rephrase this it makes no sense to me

Post by **NISMObuttnutz** » Mon Sep 01, 2003 9:47 pm

blk90s13 wrote:10) Now there will be a plug with 2 wires in it on the KA chassis harness, one being white and the other being black/yellow. Find the black/white wire on the other RB plug and connect the two.

can someone rephrase this it makes no sense to me

There is a plug with 2 wires, there is a black/yellow wire, and a white wire, that is on the 240sx chassis harness, there is a male end of that plug on the RB lower harness, with a black/white wire, connect the Black/yellow to black/white thats for your starter

Post by **Carl H** » Mon Sep 01, 2003 9:47 pm

PROJECTRB240SX wrote:ACTUALLY THE RB20DET'S THAT WERE IN THE GTS-4 MODEL R32S DIDN'T HAVE THE RB20 STAMPED ON THE TIMING COVER.

funny.my rb20 doesnt have 'rb 20' on the belt cover.had a 5 spd manual on it.didnt have any altessa bits nor hubs for 4wd on the front.

*edit*also my engine came from a 93 with grey faced gauges.

Post by **PROJECTRB240SX** » Mon Sep 01, 2003 9:47 pm

OHH NO I KNOW THAT THE LATER MODEL RB20DETS DIDN'T HAVE IT EITHER.... I WAS JUST SAYING THAT ALL THE GTS-4 MODEL RB20DETS I'VE SEEN DIDN'T HAVE THAT STAMPED ON IT EITHER.

Post by **Yellow4g63** » Mon Sep 01, 2003 9:47 pm

can't get my temp gauge to move or the Tach. I tried splicing from the RB white plug near the ecu to the KA plug and nothing. How did you guys do it? right off the ecu?

Post by **sileighty89** » Mon Sep 01, 2003 9:47 pm

splice the blue/black wire from the rb white plug into the blue/black wire from the ka plug, the tach wire is on the same rb plug as the temp wire its the one colored a light shade of green with silver stripes. the ka tach wire is the same color and on the same ka plug as the temp wire. i

Post by **sileighty89** » Mon Sep 01, 2003 9:47 pm

make sure that you have the grounds on your cluster connected to ka harness.

Post by **Yellow4g63** » Mon Sep 01, 2003 9:47 pm

sileighty89 wrote:splice the blue/black wire from the rb white plug into the blue/black wire from the ka plug, the tach wire is on the same rb plug as the temp wire its the one colored a light shade of green with silver stripes. the ka tach wire is the same color and on the same ka plug as the temp wire. i

Ahh I used Green with red stripe I think but I know I didn't use any Green with silver.

Post by **Carl H** » Mon Sep 01, 2003 9:47 pm

that doesnt make any sense.the tach and temp wires are the same for both harnesses.you need to connect the grounds else it wont work.

Post by **Yellow4g63** » Mon Sep 01, 2003 9:47 pm

There was a black wire on the RB harness plug too I assumed that was the ground. I'll cut it and run it to a diffrent ground wire then.

Post by **sileighty89** » Mon Sep 01, 2003 9:47 pm

ill take pictures of my harness and post them when i get off work today.

Post by **NISMObuttnutz** » Mon Sep 01, 2003 9:47 pm

The temp sensor wire is Blue/Black, not green. I didnt' have to connect any ground on mine to get them to work. There are 2 white plugs that have the correct color wire for the tach, the one you need is the smaller plug with less wires in it. I ran a wire from that plug right to the back of the cluster and spliced it in there rather than at the plug, worked first time.

Post by **Andrew85cm** » Mon Sep 01, 2003 9:47 pm

Well I ran it just as said above with Yellow and red and the blue and black along with the grounds and it still doesn't freakin work. I'm probably going to get a aftermarket temp and tach and see if they will work. I assume they are run on the same wires.~ANDREW~

Post by **gani** » Mon Sep 01, 2003 9:47 pm

why dont people make the wiring to the rb20 easier for themselves and just use the ka lower transmission harness and youll just have to hook up a few wires.

Post by **Yellow4g63** » Mon Sep 01, 2003 9:47 pm

He is right, On the RB harness small white plug not the big one. Yellow/red RB to Yellow/red KA, Blue/Blk RB to Blue/Blk Ka and it will work. I tried to use my KA temp sensor that had 200,000 and it wouldn't work so I swaped back the RB and it's reading now.

Post by **blk90s13** » Mon Sep 01, 2003 9:47 pm

sileighty89 wrote:ill take pictures of my harness and post them when i get off work today.

i am still waiting on those pics

Post by **Carl H** » Mon Sep 01, 2003 9:47 pm

if you are going to use the ka cluster it is much easier to run the ka lower harness.even if you use the rb lower its not hard to splice in the proper wires much less the reverse lights.

The RB20 Wiring Thread

The RB20 Wiring Thread

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