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Need help wiring sr20det Into ke55 corolla


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Hi all, i am up to the point were i want to start wiring my Sr20 engine harness to my ke55 body loom, for those of you who have done it or know whats required able to fill me in with what wires i need to connect to get the motor running, also have an external fuel pump which needs to be connected too, thanks and hope to here from someone soon 


Edited by NathanKEnut
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  • 2 weeks later...
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You should have all these plugs, and life will be easier if you also have the plugs that go into these.  So the chassis loom with wires cut off 100mm long. I used stacks of junction strips which was simple to do and I planned to replace them with neater wiring.. sometime.

Then you'll need a full engine wiring diagram and ECU pinout to find out which plug goes where and does what.

You will end up using relays to run fuel pumps, electric fans, & powering ECU stuff. I ook a COR relay box out of a random Diahatsu & used that for circuit opening relay, fuel pumps, engine fan & whatever.

SR20 plug layout.jpg

SR20 plug layout B.jpg

DG COR for 4AGE.jpg

DD Daihatsu fusebox.jpg

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That's brilliant, but also daunting, when you consider how much time is involved.


However, a simple engine swap, is not as big a job, as our two friends at Binky project undertook, with a "complete" electrics swap.

An engine swap project can go very sour, if the electrics are wired in roughly, besides not looking professional. Unreliability is the result, & your NRMA or RACQ roadside man is not going to be a great help, if your car won't go, on the side of the road, in the middle of nowhere.

Having done several wiring harnesses, where I have made them up from scratch, the secret is to do one bit at a time, & don't rush it.

One of the big advantages of making up your own harness is, that you can increase the size of the wiring used, which reduces voltage drops in the system.

Cheers Banjo



Edited by Banjo
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Lets not get a head of ourselves here. what is all this diahatsu fuse box business. don't need to be that complicated. 

SR20 looms are very easy to wire in, they wire them into anything and everything. I cannot recall the specifics, you are going to need to do your own research and study wiring diagrams.  but there will be a few grounds to connect to to the engine/body, a constant power and switched ignition wire to the ECU. Do this using the OEM corolla wiring as much as you can. afterall there was already an ignition relay and fuse box in the corolla, just use this one. 

You are going to need to install a new relay for the fuel pump, and there is an output on the ECU for the fuel pump. You need to research how to wire up a relay and find the output to the ecu to switch it on. Make sure you istall a fuse. 

Realistically that should get the engine started. 


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Those relays are in the relay box-  the circuit opening relay that cuts the fuel pumps in a smash, the fuel injection relay and the electric fan relay.. that's why I used it.   If it wasnt Diahatsu it would've been whatever the next car was in the junk pile that I looked through, so any car with a fuel injection relay box will do.

You can wire it up from scratch with Supercheap relays, but its a lot of work and ends up pretty untidy, like when I did my own headlight relay system.

If you have the original engine loom you're well ahead.

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Thanks guys for the replies, appreciate the tips and tricks, budget is the main issue at the moment so if i can properly wire the car up my self that would be a score, I've been downloading manuals and diagrams trying to find the best ones that i can understand, il take my time to do it right so no dramas a cure down the track, be patient is the key to this i guess haha. Again thanks for your replies

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Quick update.. i have installed

36- red/black wire to ignition on

34- orange/blue to START

ECU grounds to body of car

car was missing the eccs relay/ecu relay which i recently picked up

just bought a fuel pump relay and connected as instructed, i used the 106 pink/black wire 

looks like ecu is not coming on, can't find any spark aswell as fuel pump not turning on. car cranks over fine. 

what am i missing?




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Have you got a wiring diagram for that particular motor at all?  I have a  couple on on the screen right now but they show different pin numbers for the same wires. Both are meant to be SR20DET.

Was it an auto that the motor/ECU came out of?? That cutout switch is another twist in the wiring.

Can you put it in diagnostic mode and see if it can read error codes?

This diagram shows 104 for the fuel pump, so unless we have the correct diagram we're pissing in the dark.


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OK, so you don't need the air con or neutral circuits.

It seems the battery permanently powers the injector resistors, the ECCS relay, the rad fan relay, the AAC valve and terminals #46 & 109

Ignition adds the coil, the wastegate solenoid, the fuel pump relay, the check engine light & terminals #36 & #34.

Is that how it looks to you?


sr20det-wiring coloured.jpg

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