I need some guidance with OBS wiring

I'm waist deep in my swap, and I have a few questions about my TBI engine harness.

I'm swapping a 2003 DBC LQ4 into my 89 k1500 5 speed. So far I have deleted A/C, evap, and cruise. From what I understand, I will not need The TBI ECM for anything. However, there are a bunch of body power wires, hvac wires and gauge wires spliced into the TBI engine harness. Do I just need to seperate these wires, and hack all of the actual engine wiring from the harness? I'm going to try to tidy up the engine bay the best I can, without removing necessary wiring.

As always, your input is appreciated.

Just to clarify, The LQ4 harness is stand alone, and it's already done.

You can remove de TBI PCM and cut all TBI engine harness except "oil pressure sender and coolant sender" You can keep the pink or red distributor wire for 12v ignition on and cranking.All the gauge wire can be connected inside the cab in the glove box try to find your electrical diagram.

I also ended up using the TBI injector + wires to supply keyed power to the PCM. Since the old PCM controls the ground to the injectors, they are always hot with the key on. Seemed like a good place to get key on 12 volts. The other keyed source for the PCM came from the old HEI ignition power wire. Works like a champ.

i didnt check the power distribution diagram before posting this and since your not having any issues i assume it might be ok, but just thinking out loud here.... since the injectors are small, im guessing they dont draw too much current so the fuse/wire is probably not that big... can it handle the load of supplying everything needed for key on power for the new fuse block??? if it just supplys power to a relay, then disreguard this but just somehting to check into...

Thanks for the info guys. One last question. Is the single wire that plugs into the top of the tbi alternator for the volt gauge? I'll probably need that too.

the real big wire you mean that has a lug on the end and is held in place by a nut?? that goes straight to the battery. thats how the alternator charges your batt and powers the rest of the car. your volt meter im pretty sure is just connected to a ign switch positve. check your diagrams out which will tell you

just checked a few diagrams real quick. couldnt find one in your year but they seem to be the same. are you talking about the brown wire? if so then yes you are correct. that does go to your volt gauge. i was wrong about the ign positive. my apologies. heres a diagram from a 91 k1500. should answer your quesion
http://i18.photobucket.com/albums/b1...1-page-001.jpg

Yeah, I was talking about the brown wire, I should have mentioned that. Thanks for the help, Kewljay.

I believe that is for the battery light. At least that's what it's for on my 93. Not sure what your guage cluster has for lights.

Quote:

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Originally Posted by Mickeymotormount

I believe that is for the battery light. At least that's what it's for on my 93. Not sure what your guage cluster has for lights.

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yup. good call mickey. i was right the first time. always go with your gut!!! i just looked at my gauge cluster diagram again and there is a battery indicator light and a volt gauge. the gauge is like i said, hooked to ignition power. the brown wire you are referring to goes to the light bulb in the dash like mikey pointed out. idk how i missed that. probably because ive worked 14hr shifts the past few days...lol

but to be honest, idk what that lamp indicates. only thing i cant think is low battery. i just dont get how it works tho. as you can see in the diagram the other side of the light goes to switched positive. what does the brown hook to inside the alternator? i assume it has to be a ground of some sort...? but when does the ground actually make a connection to power the lamp? when the alt fails? anybody know how this works?

oh and disreguard my post #5. i thought he was talking about powering the fuse block with the injector wires. but all he was powering was the pcm which im sure draws next to nothing. so injector positive should be just fine for the pcm.

I'm still scratching my head on this one too. Does anyone know where I can hook this brown wire up to, to retain my battery light?

I guess it would depend on what year your swapped engine is. Mine is a '99 and uses one wire on the alternator. Later years used more than one wire to feed the PCM and the idiot ligtht.


After doing some research, I found that the idiot light is actually a feed to the alternator. There is a whole description in the service manual on how the system works. But for now, the info you need is that the brown wire goes to the "B" terminal on the alternator plug. Below is a schematic. This info is out of the '99 GM service manual. I believe this should work for you.



http://i488.photobucket.com/albums/r...s/scan0285.jpg


http://i488.photobucket.com/albums/r...s/scan0286.jpg

Thanks Mickey. I appreciate it, man!

If I don't hook it up, would the battery light stay on, or off?

I don't really need it, but if it stays on, that would be kind of annoying.

If you hook it up, the light should go out. Depends on the year of swap engine though. Like I said, this schematic is from the '99 GM service manual. Different years could be different. It's worth a try.

Yeah, mine is from an 03 express van. It is a bit different. Terminals a and f are unused, b is red, and c is brown. I'm willing to bet either one would work.

Try the brown one. You may just get lucky!!!!!.

One last question. I have a stand alone harness with it's own relays. It just needs a fuel pump control ran to the relay, constant 12v from the battery and a keyed 12v source.

Can I snip off the TBI fuel pump relay and use all of those wires to power the new stand alone set up?

I'm pretty sure the gray wire will control the fuel pump, and the pink wire would be a good keyed 12v source. Please correct me if I'm wrong.

If I understand your question correctly, I don't think you can use the original fuel pump relay control wire from the original PCM. I left my original PCM in the truck thinking it would be able to power my original fuel pump relay. This setup doesn't work because the original PCM doesn't "see" any crank or cam signals from the new engine. So, all it does is prime the system. After 2-3 seconds, it stops power to the fuel pump relay because the old PCM thinks the engine stalled since it "sees" no signals.
So, this is not a viable source of keyed 12V since it's controlled by the old PCM. Hope this helps.

the gray wire is what feed the power from the relay to the fuel pump then across from that one there is an orange wire that supplies power to the relay, there should be a green wire with a white tracer that is the relay control from the pcm and a black with white tracer for ground. There might also be a red wire with a connector on the old relay but dont worry about that one. That is only to jump the relay if you had to. What I did with my fuel pump relay was use the relay from the truck and connect the fuel pump relay control wire from the new pcm and connect it to the control on the old relay.

Thanks for the info everyone. I appreciate it. I got the old bastard running this morning. I just have to work out a few bugs now

Sorry
But how did you end up hooking up to the alternator?
Im using the alternator from the donor truck and of course has a different plug connector. Do i just cut the original connector or use the 90's model alternator?

No need to apologize, man. What I like about this board is how everyone helps each other out.

I actually didn't hook it up to anything yet. The battery light wasn't illuminated so I just left it go. If it comes on or there are any adverse problems, I'm going to try connecting it to the brown wire that plugs into the top of the lq4 alt.

When you do your lsx harness, just make sure you don't clip off the alt plug

Look in my sig and you will see a link to the 6.0 service manual if you need it for anything.

Thanks guys
I went ahead and managed to get the original alternator on there.