2007 LQ4.

If you look at sites with information like
http://lt1swap.com/E38%20ECM%20Connector%20Pinouts.htm

How do you know if it will work with YOUR exact model engine.
example
Link says "Below are the ECM Connectors for 2008 vortec 5.3L harness. Should be similar for 4.8L 6.2L applications. "

But have a 2007 LQ4 from a hummer.
What if wire#24 isnt a fuel pressure in that model - its actually something else ......... *shrug*

How are you guys approaching this if its not a direct pinout for your year/model.

Trying not to spend 20 hours to find it doesnt work.

 

Anyone ?

 

What vehicle is the LQ4 going into? The answer to that question will help to identify what to keep on the harness and what you can delete/ignore.
If you are uncertain about a wire or a pin when looking at a diagram, you are going to have to trace each wire using a multimeter (set to continuity). That's what I had to do with my first ever harness adaptation. Main thing to do is to identify the major circuits of the engine hareness that allow the engine to function properly (PCM, injectors, coils, MAF, o2's, etc.) Pay special attention to pink, orange, and black wires when you are testing for ignition power and ground.

 

57 Chevy truck.

So need to keep the fueling (inj) and TAC (throttle) and transmission and normal engine functions (cam/crank) etc

 

What I would do in your situation:
Unloom the entire engine harness, you'll likely want to have it rewrapped anyway in the new engine bay when it's all said and done. Identify each and ever sensor/component on the engine that you are going to use after the transplant: MAF, injectors, coils, o2's, TPS, MAP, crank sensor, cam sensor, temp sensor, oil pressure sensor, transmission pigtail, etc. Follow each sensor to either a PCM connector, harness connector, or loose wire end and label said wire. That will give you the back bone to the harness connections. After that you'll need to identify all of the power feeds (I believe the PCM has two ignition feeds and one straight battery feed, injector banks each have an ignition feed that is shared by the coils. The MAF and the front o2 sensors also share an ignition feed if I am not mistaken. Also the transmission has an ignition feed) After the power feeds you'll need to address the grounds (each of the things that you identified when locating the power feeds will likely have a corresponding ground that needs to be properly addressed. Lastly you'll have to identify all of the gauge signal wires (Tach, oil pressure, temp, VSS, etc).

I know I am probably over looking a few things, but that should get you started in the right direction. After you identify all of the aforementioned items, the harness should appear to be getting less confusing. Take your time and label everything and only cut/remove wires that you have double and triple checked either with a multimeter or a diagram.

 

Thanks.
The problem would be a wire or circuit that I would not be sure if its required or not.
eg

Yellow 39 - Starter Enable Relay Control

I would have no idea if thats actually required by PCM to enable siglan to starter. According to LT1 can be removed.

 

What I would do is label everything you can. Hook up the sensors and gauges that I mentioned above. The wires that you are unsure about, move them out of the way, but do not remove them completely until you get the car running and sorted. When I do a swap, I try to keep the engine/trans/PCM as a stand alone system, seperate from the chassis harness and circuits of the car. I will usually try to retain the fuse block assembly from the donor car so that I will have to tap into the chassis harness as little as possible, just enough to feed the new engine harness the appropriate ignition power. So circuits like the starter relay and fuel pump relay, etc will remain originally wired in the transplant car. To reiterate, just take your time.

 

Brendan has covered the conversion quite well and countless folks have used only his information to modify their harness.

I bet if you list the circuits you are concerned about you will get clear answers, but yellow is "remove" and you could either leave them alone as suggested above or un-pin and save them.

You have a blue/green harness, correct?

 

the starter relay is there to allow the "pcm" to actually start the vehicle. It is not required. You can use your trucks starting circuut and ditch that function if u like. I did on my 92 s10...

 

Thanks ..... I started today ...... sorry been a busy few weeks/month - built my first 4l60e inbetween



But now .....




So long story short ........ follow the depin instructions from LT1swap.com ......
http://www.lt1swap.com/2003-07pcmpinouts.pdf

and then extend a fuse box for fused power control similar to
https://www.bp-automotive.com/produc...i-24x-engines/

Leads to a few other questions.


How are most people controlling fans for cooling ......... meaning via the PCM - or static switch(on/off) just linked to a temp sensor ?
Any considerations with AC in terms of the harness itself.

Any links to someone who has done it in a build with detail or goes over it ?

all new to me.

 

Fakky, I too am about to start on this exact same venture. I suspect mine will be a little easier, with far fewer wires than yours though. Mine is DBC so no TAC module, or gas pedal wiring to deal with. I will be setting up a 0411 PCM, and GM harness as a stand alone controller for a 5.3LS & 4L60E trans going into a '70 Chevrolet C-10. I'm literally waiting on the PCM & harness to arrive so I can start hacking it up. My plan is to move the PCM inside the cabin (under the dash) and to hide as many wires under the intake manifold as possible.

I appreciate you guys posting the links above.

 

I hope I'm not post-hogging here. Just wanted to say that I un-bundled the entire harness today, and have only the following items laid out on the engine at this time; L&R coil wiring, L&R injector wiring, TPS, IAC, ECT, alternator, Cam pos, oil pressure, & crank position, transmission section, & starter wire (purple)... It REALLY reduces the amount of wires you have to run.

On the trans harness I combined the NSS wiring, the speed sensor, and both front O2 sensors. Now, instead of running down the drivers side frame rail I have the trans section running straight down the center of the trans. REALLY cleans up, and significantly shortens that harness. It went from 5' down to 2.5'. I am going through the firewall right behind the oil pressure sending unit with computer mounted under the dash, on the firewall. It's taking a LOT longer than I thought it would. I spent almost 3 hours removing loom, tape, marking wires with tape & marker, and un-pinning from the connectors... Ugh... Now tomorrow I should actually be able to mount the PCM and start re-pinning everything that will be used.

 

Nice - no glad to have someone in here.
Im not as far along ...... basically deloomed and started depinning the C1+ C2 connectors for lt1swap. Mostly the emissions stuff obviously.

Got stuck on the TAC module.
Think on non DBW trucks you normally have .... next to the PCM fuse block..... C100, C152,C153 connectors .......

Mine has DBW and has what looks like C100 and C152 omly but then C152 (black) has 1-2 wires that go into the TAC connector........ so typically I think C100/C152 are totall removed - but not sure I can on a DBW/TAC setup.

 

I wish I could help you but I have ZERO experience with DBW/TAC set ups. I always use DBC for the simplicity. I found this;
http://chevythunder.com/drive_by_wire.htm maybe there is some information there that can help?

 

No worries ....... thinking Im making some progess - was just 1 wire that had me confused but think its related to CRUISE. Joings back to one of those other connectors.
Thanks for link.

Did you completely unpin all of the harness - you said REPIN ...... wowza -
I made a rookie mistake and ripped my harness off the engine before labelling. Nothing like spending 4 hours with a multimeter OHM out wires to check what that sensor (x) is and labelling after the fact. Oh well.

Yes taking longer than I thought also ....... a few hours here .....a few there ...... making progress though.

Anyone know if the fuse block for ignition wires (C2) for later years available anyhere ..... not sure mine marries up with the 2002 one on LT1swap etc

 

Yes, I removed every pin/wire from both connectors, and then separated out all the connectors so I could lay them separately on the engine for routing purposes. For example-the alternator exciter wire, alternator charge wire, ECT, TPS, and IAC are now all tied into a mini-harness and go under the intake manifold straight to the back of the engine. I tied the engine coils & injectors on each bank into separate harnesses that join together at the back of the engine. Tied the trans connector, VSS, neutral safety switch, and both front O2 sensors into one mini-harness that runs up the center of the trans to the back of the motor. It's so much easier to separate them all out, removing what you don't need to use. This way, I can shorten, or lengthen each wire as I go and be able to see the exact wire I'm working with without having to OHM every wire out. Yes, it's a lot of work... But I'm putting the computer inside the cabin to try and clean it up under the hood. The MAF wiring is proving to be a pain in the butt.. Kind of hard to hide it due to it's location, and the length of the wires that I have to attach to it to try and hide it. I'm thinking I'm going to run the wires for the MAF UNDER the intake tract (using factory intake tract and air box from a 2002 Silverado), and tying it in with the alt, TPS, IAC wiring running under the intake manifold.

I did not mark the wires locations when I removed them either.. But, I have another assembled harness that I can use to verify that I have everything correctly placed, and I'm using pinout diagrams from LT1swap to get it all together. It's not something I will do again. Next time I will just buy the after-market stand alone harnesses. The amount of time I have in this harness so far I could have bought the after-market harness and be working on other stuff...

 

Hey. Yep kinda of in same boat - starting to think it if it was worth it. Only problem is so far I have done everything in car myself ...... so really trying where its possible to continue that theme. Only one way to learn. Have to agree though once done it - not really worth the $200 (You have to spend $100 on parts to go standalone anyway) to spend the time. Am sure its much quicker next time around.

Thats neat that you did all that - I didnt quite have the confidence to pull it all apart ............ just depinning what I dont need ..... add the 2 AC signal wires etc

 

Another question more of a curiosity one .....

Why do the AC and the Oil sensors get decoupled. I know the oil sensor is not used by the PCM - but figured that the signal could still be used for aftermarket gauges etc ?
AC Im not sure how that sensor is used within the harness and PCM.

 

When you say "decoupled", do you mean removed from the harness? I removed all the A/C wiring because I'm putting a stand alone, after-market A/C system into the truck that does not need to interface with the PCM in any manner. I am still running the factory oil pressure sending unit and it is still tied into the PCM. The after market gauge cluster I'm using should still be able to use the signal. If it can feed the dash gauge, it should be able to feed the after-market gauge as well.

 

Yes decoupled as the sensors fully removed. From memory

Oil Pressure/ Oil Level and AC are depinned and removed.
eg7GRY27055 Volt Reference (OIL PRESSURE) 45GRY27005 Volt Reference (A/C)63BLK2755Low Reference (OIL PRESSURE SENSOR) 14RED/BLK380A/C Refrigerant Pressure Sensor Signal (A/C)
43DK GRN/WHT459A/C Compressor Clutch Relay Control (A/C)
** ALL depinned and corresponding sensors removed -> http://lt1swap.com/2004vortec_pcm.htm

My understanding is the oil pressure doesnt send a signal via PCM .......... thats the reason its decoupled ......... then use an aftermarket etc.

My question is mainly around why do you need to - couldnt the same wires/signal and sensor be used for integration to aftermaket gauges/AC systems etc.