I am building a harness for my lsj swap into a toyota pickup and have a few questions about what the pin out means...

I am using this diagram Service Information and on the first plug

#13 engine main relay fused control (4)
#38 engine main relay coil control
I am confused with these 2, I have an assumption but hope to hear from someone who knows...

#18 accessory voltage is this power input from ignition turned to accessory?
#19 run/crank ignition 1 voltage Is this a power input from run/crank on the ignition?
#20 battery positive voltage Is this a constant from battery no switch?
#40 check engine indicator control Does this power the check eng light? power or ground?


Also in the #3 plug
#15 oil pressure switch signal I know it goes to the sensor on the oil cooler but what does it do? Is it just for a gauge or does it tell the comp if pressure is low for check eng light?

Thanks for any insight you may have...

 

#13 engine main relay fused control (4) fused wire that would go to the switch side of the main relay (pin 30 on a relay)
#38 engine main relay coil control wire that controls the coil side of the relay (pin 85 on a relay)
I am confused with these 2, I have an assumption but hope to hear from someone who knows...

#18 accessory voltage is this power input from ignition turned to accessory? Yes
#19 run/crank ignition 1 voltage Is this a power input from run/crank on the ignition? yes
#20 battery positive voltage Is this a constant from battery no switch? yes
#40 check engine indicator control Does this power the check eng light? power or ground? I would assume it is exactly what it says. Controls the CEL on or off. More than likely gonna be on the power side of the light.

 

Awesome thanks tstone!

Now just the oil pressure switch and I'm good to go...

 

Post picks of said truck

 

Well we don't have an OP gauge so I guess you kind of answered your own question
Now go get that truck done and come back with some pics

 

LOL , I guess I'll have to check the inside of one out some day, I had no idea there was no gauge. Thanks for your help, I can finish he harness and move on now. I got a couple pics. Let me see if I can get them posted...

 

Pic fail


but yeah it's very exciting...............

 

fixed.

 

Is it mounted in?

 

Yea, I still have to pull it a couple more times to get the firewall built but the motor mounts are done.

I have a question about the grounds. Some say chassis ground and some say signal ground, Do I hook all the chassis grounds together and ground it somewhere and all the signal grounds together and ground somewhere else? how much separation is necessary? Or if I'm wrong on my assumption whats the deal on the different grounds?

 

Hmm.... do you have the pcm pinout? I'm not sure if they go back to the pcm and then the pcm grounds them, or not...... As far as the chassis grounds go, i'd just ground them to the chassis lol.

What are they actually for? the signal grounds.

 

signal grounds are the ground wires from the sensors, they go back to the pcm. chassis grounds go to the chassis, or better yet hook them to the block and a good ground from the block to the chassis.

the check engine light is a ground output. supply 12v+ to one side of the check engine light and hook #40 to the other side of it.

 

Thanks Sharkey, Do you know if the electric fan control is a ground source also? I have a fan controller and the signal wires to the relays need to be grounds like the check eng light.

In the harness all the chassis grounds go to one terminal to be bolted to the block or wherever and the signal grounds go to another terminal that looks as if it was also bolted somewhere it also has the large ecu signal ground in it. Maybe someone can look at a car and see where the two are bolted, black is chassis ground and black with white stripe is signal ground. Im assuming they both get grounded but have to be separated to avoid ground noise but how far apart?

Thanks for all the help getting me past the electrical ****

:EDIT: I am wondering now if all the coil control wires (fuel pump, coolant pump, fan and main) are ground sources instead of 12v?

 

generally pcm outputs are grounds on gm stuff. i know for a fact that the fuel pump and fan outputs are ground. and as long as you keep those grounds seperate you will be fine.

 

Thanks again Sharkey and Tstone, harness is done

 

Awesome. You better post some progress pics!

 

So I thought I had it all figured out and got to thinking last night, The wires from the ignition to the ecu (accessory, run,crank) are these ground signals from the ignition or 12v? I'd hate to hook up 12v if they're suppose to be grounds...

I got a Tsudo header from flea bay for $60 shipped and cut it up to fit in the truck... Looks neat, hope it works as good as it looks.

 

Do you know how to read a schematic? Serious question, not sarcastic.

 

I'm not an electrical guy but if I had one I'm sure I'd figure it out. A friend sent me one from alldata but I cant see it and it gets all distorted when I zoom. I know I can buy a haynes or whatever... Do you know of one I can download?

I am use to the toyota stuff since that's what I have been messing with for a while(this truck and a supra) and all the signals for relays etc are 12v instead of ground so I am just making sure I don't let the smoke out of the ecu. lol

I am far from a pro and probably beyond my ability's in the electrical aspect of this swap but have more time than money and not afraid to learn something.

You have been great help so far.

 

Reason I ask is because I can give you my AllData log in info and you can get what you need from there. I'm sure you can figure it out.

 

ooohh!! yes please! That would be awesome.

 

also just so your aware with alldata you dont need to pay huge money to use it. with alldata diy for around $20 per car you can access the same info as anyone with the full alldata membership.

 

PM'ed ya with the info

 

This is exactly the info I need !!!!!

For Powering the Harness, Mine’s a track day car.. A Miata. I have a big power switch, and push button Starter. I don’t have an accessory stage.

Im trying to work out, which wires I power (constant - keep ecu heartbeat when key's off), which wires I power when engine is in ON position.

Do I need to power these.. like this ?

#13 - When I turn my power switch on, then I power this.
#19 - When I turn my power switch on, I also power this, NOT the starter button is that correct ?
#18 - I don’t have an accessory mode, should I power this with #13 (tie them together) or do I not need it ?

#20 - Battery side - always ON/constant power.

#38 - Do I power this (I’m about to trace the loom to work this one out), if so only when the power’s on ?

 

13 will be your power wire to the Engine main relay.

38 will be the ground circuit for the coil side of the engine main relay, therefore turning the relay on.

If you wanted, you could just constantly ground the relay (38) and have power go from your "big power switch" to 13.

18 & 19. I would send power on that wire, to the pcm, from your "big power switch"

20. straight from battery positive. No need for a switch.