ECM Computer Condrum - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Accelo** · 06-08-2021, 06:20 PM

I have transplanted an LS1 and had the original Corvette harness modified. I am now stuck with the wiring lengths unless I want to start over with a new custom replacement harness. If I would have planned better that would be my recommendation to anyone else. My question is where should I install the ECM? I have pictured the location that seems to work best for my wire lengths. The hood hinge doesn't interfere at all with this location. I will paint it to match the firewall, maybe that will help? I plan on installing the ODB connection in the glove box. Well, what is left of the box after installing the Vintage Air. Another option is to install the ECM under the passenger bucket seat. The is possible but the large hole that would be required to install it under the floor has me turned off. Those seem to be my best options without changing the harness.
Regrettably the existing wiring is too short to put it behind the headlights on the core support. I would much prefer it out of sight.
Maybe I have answered my own questions? Comments appreciated.
Rick

**A1971Blazer** · 06-09-2021, 08:42 AM

Don't have mine that far yet but.....
I have an LS1 out of a 02 TransAm and the original harness as well and will be in about the same location as yours along with the cruise module.
I found a plastic PCM cover from a Tahoe that I plan to use to somewhat "hide" the ugly PCM...
Mine isn't going to be a "show" truck and I'm not as concerned about how it will look under the hood...although it will be neat and organized.

Bigdav160 · 06-09-2021, 10:32 AM

I might be the only one but I don't mind lengthening and shortening wires

gmc684x4 · 06-09-2021, 10:47 AM

If lengthen wires figure out length needed and do one wire at a time less likely to accendently mix them up

Davidf · 06-09-2021, 12:14 PM

Quote:

Originally Posted by gmc684x4

If lengthen wires figure out length needed and do one wire at a time less likely to accendently mix them up

I agree, and stagger the splice connections so you don't end up with a big lump in the harness.

BigBird05 · 06-09-2021, 06:40 PM

I have over 25 years of experience making harness's. It is not that hard to do if you take your time and label every wire. Get a donner harness from a pick a part so you use the exact same color / striped wire. Strip the wire about 3/4 of an ". Put the shrink tube over one of the wires. Use flux on both wires, twist them together, heat the wire with a good quality iron ( this is no time to get cheep ) and apply the solder. Then cover the splice with shrink tube. You need to space the solder joints so no solder joint overlaps another one. If you go this route you can PM me for more information. You will be happier if you take the time to mount the PCM in the place that you want it than to compromise on the location.

Steve Cole · 06-09-2021, 10:33 PM

I think it is fine where you have it. Paint it to match the body color and it will be good.

**Accelo** · 06-10-2021, 02:06 AM

I want to thank everyone for the encouragement. I have decided to leave it where it's at. Some part of me wanted to mimic some of the high end builds where everything is cleaned up and hidden. My hat is off to them as the about of work it takes, to pull that off, is nothing short of astounding. I would like to drive my truck this summer even it it's late summer. So keeping the computer in the open is just one of the compromises I will make. The engine compartment is getting pretty busy with relays, fan and air-conditioning. Guess one more item will make little difference in the overall picture.
Thanks
Rick

06-08-2021, 06:20 PM	#1
Accelo Senior Member Join Date: Mar 2015 Location: washington Posts: 2,295	ECM Computer Condrum I have transplanted an LS1 and had the original Corvette harness modified. I am now stuck with the wiring lengths unless I want to start over with a new custom replacement harness. If I would have planned better that would be my recommendation to anyone else. My question is where should I install the ECM? I have pictured the location that seems to work best for my wire lengths. The hood hinge doesn't interfere at all with this location. I will paint it to match the firewall, maybe that will help? I plan on installing the ODB connection in the glove box. Well, what is left of the box after installing the Vintage Air. Another option is to install the ECM under the passenger bucket seat. The is possible but the large hole that would be required to install it under the floor has me turned off. Those seem to be my best options without changing the harness. Regrettably the existing wiring is too short to put it behind the headlights on the core support. I would much prefer it out of sight. Maybe I have answered my own questions? Comments appreciated. Rick Attached Images

06-09-2021, 08:42 AM	#2
A1971Blazer Senior Member Join Date: Nov 2013 Location: East Tennessee Posts: 2,198	Re: ECM Computer Condrum Don't have mine that far yet but..... I have an LS1 out of a 02 TransAm and the original harness as well and will be in about the same location as yours along with the cruise module. I found a plastic PCM cover from a Tahoe that I plan to use to somewhat "hide" the ugly PCM... Mine isn't going to be a "show" truck and I'm not as concerned about how it will look under the hood...although it will be neat and organized. __________________ 1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer .............

06-09-2021, 10:32 AM	#3
Bigdav160 Registered User Join Date: Apr 2011 Location: Klein Texas Posts: 3,852	Re: ECM Computer Condrum I might be the only one but I don't mind lengthening and shortening wires __________________ My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe

06-09-2021, 10:47 AM	#4
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	Re: ECM Computer Condrum If lengthen wires figure out length needed and do one wire at a time less likely to accendently mix them up

06-09-2021, 06:40 PM	#6
BigBird05 Registered User Join Date: Aug 2019 Location: Cheraw Posts: 1,300	Re: ECM Computer Condrum I have over 25 years of experience making harness's. It is not that hard to do if you take your time and label every wire. Get a donner harness from a pick a part so you use the exact same color / striped wire. Strip the wire about 3/4 of an ". Put the shrink tube over one of the wires. Use flux on both wires, twist them together, heat the wire with a good quality iron ( this is no time to get cheep ) and apply the solder. Then cover the splice with shrink tube. You need to space the solder joints so no solder joint overlaps another one. If you go this route you can PM me for more information. You will be happier if you take the time to mount the PCM in the place that you want it than to compromise on the location.

06-09-2021, 10:33 PM	#7
Steve Cole Registered User Join Date: May 2012 Location: Faith,NC Posts: 1,626	Re: ECM Computer Condrum I think it is fine where you have it. Paint it to match the body color and it will be good.

06-10-2021, 02:06 AM	#8
Accelo Senior Member Join Date: Mar 2015 Location: washington Posts: 2,295	Re: ECM Computer Condrum I want to thank everyone for the encouragement. I have decided to leave it where it's at. Some part of me wanted to mimic some of the high end builds where everything is cleaned up and hidden. My hat is off to them as the about of work it takes, to pull that off, is nothing short of astounding. I would like to drive my truck this summer even it it's late summer. So keeping the computer in the open is just one of the compromises I will make. The engine compartment is getting pretty busy with relays, fan and air-conditioning. Guess one more item will make little difference in the overall picture. Thanks Rick



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