GMT400 to LS Harness Questions

[95SUBURBANLM7]

it depends on your engine/trans/pcm/tcm combo, your harness, and your truck. for most ls swaps to INTEGRATE it into a gmt400 is no different than if you are installing it into a 55chevy chassis or a Porsche 911 conversion.... usually is 3 or 4 wire hookup no matter the chassis. the gmt400 chassis is really straight forward and a easy swap. the guy above is giving you useful good info for your gauge cluster. and yes I have installed ls swaps into a 55 chevy nomad, also in 7 porsches, 4 gmt400's, 69 Camaro, rx7, and so on... they are fun and easy swaps. do your homework as most swaps are straight forward but I have not found any 2 installs exactly the same. but most of all have fun and enjoy.

Yes the physical swapping in of the engine is easy, but SEAMLESSLY (so it looks as factory as possible) integrating the two harnesses is a different story. I can tell you now, it's not a three to four wire swap. From what I am looking at, there are fifteen wires on the old harness that need to be connected to twenty wires on the LS harness.

Here is what I am talking about.
PLEASE REMEMBER THIS IS FOR A 1995 MANUAL TRANSMISSION EQUIPPED SUBURBAN. If you have a 1995 Tahoe/Silverado, the pinouts are probably 99% similar. I dont know about an A/T equipped vehicle and quite frankly, I really dont want to.

GMT400 Blue ECU Connector "E" Side:
E6 - MIL - BRN/WHT
E12 - A/C Signal - DK GRN (By "signal", Im guessing this is letting the ECU know that the A/C is on?)
E13 - Brake Signal - PPL (Again, I assume this is to let the ECU know that the brakes are being appied?)
E15 - Ignition Feed - PNK (Power only when the ignition is on, except when cranking)
E16 - Battery Feed - ORN (Constant power, at all times)

GMT400 Blue ECU Connector "F" Side:
F6 - Fuel Pump Relay Control - DK GRN/WHT
F8 - 4WD Low Range Signal - GRY/BLK
F9 - Serial DATA - TAN
F13 - VSS - DK BLU
F15 - Ignition Feed - PNK
F16 - EVAP Canister Purge Control - DK GRN

GMT400 Red ECU Connector "B" Side:
B8 - ECT Signal - YEL - GRY
B10 - Cruise Signal - LT BLU/BLK
B12 - Fuel Pump Signal

There is the black connector, that goes to the DRAC, but I do not have and connot find the pinout guide to it. If anyone has one, please let me know ASAP.

LS Harness ECU Blue Connector:
19B - Ignition 1 Voltage - PNK (Im guessing that this is the same as "Ignition Feed" on the old harness.)
20B - Battery + Voltage - ORN (Again, Im guessing, that this is the same as "Battery Feed" on the old harness.)
33B - TCC Brake Signal Switch - PPL
35B - CPP Switch Signal - GRA (Clutch Signal Switch???)
57B - Battery Positive Voltage - ORN
58B - ECM/PCM/VCM Class 2 Serial DATA - DK GRN
75B - Off/Run/Crank Voltage - PNK


LS Harness ECU Red Connector:
9R - Fuel Pump Relay Control - DK GRN/WHT
10R - Engine Speed Signal (TACH) - WHT
15R - Charge Indicator - BRN
16R - 4WD Low Signal - GRY/BLK
17R - A/C Request DK GRN/WHT
19R - 4WD Front Axel Switch BLK/WHT
20R - VSS Low LT GRN/BLK
21R - VSS High PPL/WHT
34R - EVAP Canister Purge Solenoid Control DK GRN/WHT
43R - A/C Clutch Relay Control - DK GRN/WHT
45R - EVAP Canister Vent Valve Control - WHT
46R - MIL - BRN/WHT
50R - Vehicle Speed Output 4k DK GRN/WHT
55R - A/C Low Pressure Switch Signal - DK GRN

Im sitting here looking at my harnesses and now the list looks incomplete. Im going to post this now and then edit it with new info here within an hour.

Edit:
Ok, so of course my list was incomplete...I completely missed the C100 bulkhead connector. I believe it is the C100, please correct me if Im wrong. This is the connector that is under the brake booster. There are about thirty six, so hang in there.

A1 - Battery Fused Feed - RED - This goes to the area where the ECU/DRAC is located.
A2 - Ignition Feed - PNK
A3 - Battery Feed - ORN
A4 - Stoplamp Feed - LT BLU
A6 - A8 - Battery Feed - RED
B1 - Windshield Wiper Motor Feed - HIGH SPEED - PPL
B2 - Accessory Feed - YEL
B3 - Windshield Wiper Switch Signal - PULSE DELAY - BRN
B6 - Check Engine Indicator Lamp Output - BRN/WHT
B8 - Air Inlet Valve Motor Feed - DK GRN/WHT
C1 - Horn Relay Output - COIL - BLK
C2 - Neutral Safety Switch output - P/N - YEL
C3 - Charge - BRN
C4 - Oil Pressure Indicator Lamp Output - TAN
C5 - Coolant Temperature Indicator Lamp Output - DK GRN
C6 - Brake Warning Indicator Lamp Output
C7 - Ignition Feed - PNK
C8 - ABS Failure Indicator Output - LT GRN
D1 - ABS Diagnostic Signal - TAN/WHT
D2 - Cruise Control Engage Signal - LT BLU/BLK
D3 - Cluster Speed Signal (Tach?) - WHT
D6 - 4WD Front Wheel Lock Indicator - BLK/WHT
D7 - A/C Switch Output - LT GRN
D8 - Ignition Fused Feed - BRN
E1 - Ignition Feed - CRANK - YEL
E2 - Ignition Feed - PNK
E3 - Battery Fused Feed - RED
E5 - Ignition Fused Feed - BRN
E6 - VSS - Signal
E7 - VSS - Return
E8 - Fuel Pump Relay Feed - PRIME - RED

There is the C100 pinout...now Im wondering why I didnt just post a picture of the pinout list. Anyway, I think that all the ones that end in "Output", are going directly to the instrument panel, the ABS computer, or the windshield wiper controls.

So there are all the pins/wires that I believe are relevant to this swap. This is why I wrote that this is not merely a "3 to 4 wire swap". Now below, I am going to list which old pins go with which new pins. I'm pretty sure I am correct, but if I am wrong, please let me know.

E6+46R
E12+17R
E13+33B
E16+20B

F6+9R
F8+16R
F13+50R
F15/E15+19B/75B/
F16+34R

B8+74B
B10+???
B12+???

 

[90W7]

Thanks for the info, lets go through it. I am reworking the LS harness per lt1swap.com. Brendan has some really great info there. Im actually gonna send him a bottle of fine Colorado ***** as a "thank you". Im reworking the Suburbans harness too, but I guess thats obvious. ;-p

I knew the ECU didnt need the oil pressure sensor (OPS), but I didnt know it didnt need the CTS or the alternator info. The OPS, I just intended on getting a three wire OPS that would fit in the stock spot without any adapters. If I cannot find that sensor, Ill just buy the Autometer part. Thanks for the part number! After that I was going to take the OPS wires and connect them to the GMT400 harness at the bulkhead in the firewall on the drivers side just below the brake booster. I read the pinout and didnt see a spot for it. Which wires do I connect the OPS wires to?

Sounds pretty straight forward for the CTS. I guess I will go the route of installing the old CTS in the right side port. I believe that will connect to a yellow wire (B8 from the red GMT400 ECU plug)?

The alternator wire, I cut it out of the GMT400 harness and am using the LS harnesses alternator plug. This is per Brendans instructions on lt1swap.com, so I believe it is right.

You answered my question that I had regarding the orange and pink wires. In the GMT400 pinout, it called pink "Ignition Feed", and orange as "Battery Feed".

Again, much appreciation for your help. You're info is helping me get my project finished before the snow starts flying!

So on the coolant temp sensors: just so were on the same page.

The TBI single wire is kept and installed on the right rear LS cylinder head like you said above (this is for your cluster gauge) I forget the wire color(im going by pictures i took and i forgot whats the factory color and what i extended) but this goes straight to the cluster, it has nothing to do with the TBI computer or LS computer.

The TBI multi wire coolant temp sensor goes to the TBI computer and is not needed(cut this out)
The LS coolant temp sensor wiring will be a part of your LS harness and does not get removed because the LS computer does need the coolant temp. this goes to the temp sensor on the left front cylinder head.


On the oil pressure sensor:

I just kept the TBI OPS wiring in the same location and used the adapter so the TBI OPS would thread right into the LS block (to me this would be the easiest route) Im not sure where these wires go on the bulkhead connector.

Now on the alternator wiring im actually confused as to how i did mine. im going to go out and check some stuff out tomorrow. I remember i eliminated the GBCM (the amp meter on the negative cable) by re pining one of the wires back to the pcm and then i forget the rest hehe ..i know my volt gauge reads and shows charging but ill have to look into it.

I hear you on the snow.. i got my truck fired up and it snowed 2 days later. so i almost ran out of time in mine(working outside).

I know i re-stated some things and hopefully answered what you asked but if i didn't just call me out and ill explain further. I don't mind helping one bit so just keep the questions coming if you have them. Post some pics if you can and another good source for information is http://www.ls1truck.com/forums/lsx-truck-conversions/

 

[95SUBURBANLM7]

So on the coolant temp sensors: just so were on the same page.

The TBI single wire is kept and installed on the right rear LS cylinder head like you said above (this is for your cluster gauge) I forget the wire color(im going by pictures i took and i forgot whats the factory color and what i extended) but this goes straight to the cluster, it has nothing to do with the TBI computer or LS computer.

The TBI multi wire coolant temp sensor goes to the TBI computer and is not needed(cut this out)
The LS coolant temp sensor wiring will be a part of your LS harness and does not get removed because the LS computer does need the coolant temp. this goes to the temp sensor on the left front cylinder head.


On the oil pressure sensor:

I just kept the TBI OPS wiring in the same location and used the adapter so the TBI OPS would thread right into the LS block (to me this would be the easiest route) Im not sure where these wires go on the bulkhead connector.

Now on the alternator wiring im actually confused as to how i did mine. im going to go out and check some stuff out tomorrow. I remember i eliminated the GBCM (the amp meter on the negative cable) by re pining one of the wires back to the pcm and then i forget the rest hehe ..i know my volt gauge reads and shows charging but ill have to look into it.

I hear you on the snow.. i got my truck fired up and it snowed 2 days later. so i almost ran out of time in mine(working outside).

I know i re-stated some things and hopefully answered what you asked but if i didn't just call me out and ill explain further. I don't mind helping one bit so just keep the questions coming if you have them. Post some pics if you can and another good source for information is http://www.ls1truck.com/forums/lsx-truck-conversions/

Correct, we are on the same page. The rear (passenger side head, rear/exhaust manifold mounting side)CTS is for the gauge, the stock CTS location is for the LS ECU.

Again, correct on the TBI OPS. Do you know of a OPS that is three wire, that fits in the LS OPS location? Im gonna take a look and if I find one, Ill post it here.

I would ask why you modified the alternator wiring, but I dont think it pertains to my swap so I'll stay silent on that. Too much info if ya know what I mean. ;-)

Yeah the temps are dropping and its just a matter of days before the snow flies here. Usually Halloween is when our first snow fall is

I appreciate you restating, it helps me as well as others that will inevitably see this post now and in the future.

 

[K30burb]

you have missed the point of the terminology of the "3 or 4 wire swap" it pertains to after you are done with your harness build... it typically is a 3 to 4 wire install at that point. typically meaning= 12v constant, 12v switched, and ground. there are more if you are doing electric fans and other mods. you are making this way too hard on yourself. sounds like you have the pinout charts for the truck and the ls swap, so just integrate them. I think you are saying you want to delete the black box ecm and install the ls pcm and utilize the trucks underhood fuseblock? so open the hood and get to it. no disrespect at all, but the more time you spend contemplating it or typing about it is time you could be building it. have fun and enjoy your install.

 

[95SUBURBANLM7]

you have missed the point of the terminology of the "3 or 4 wire swap" it pertains to after you are done with your harness build... it typically is a 3 to 4 wire install at that point. typically meaning= 12v constant, 12v switched, and ground. there are more if you are doing electric fans and other mods. you are making this way too hard on yourself. sounds like you have the pinout charts for the truck and the ls swap, so just integrate them. I think you are saying you want to delete the black box ecm and install the ls pcm and utilize the trucks underhood fuseblock? so open the hood and get to it. no disrespect at all, but the more time you spend contemplating it or typing about it is time you could be building it. have fun and enjoy your install.

I guess I did, and that's where I was getting confused. I saw all these wires and thought, "3-4 wires???". Correct, I'm looking to completely remove the old ECM and just let the LS take care of it all.

I'm doing just that, getting to it. No disrespect taken at all.

 

[super10brss]

Yeah no problem. I've yet to do my speedo but when I do plan on taking pics and what wire needs to go to what. Your not on agearhead4life Facebook group are you?

Sent from my throttle body injected galaxy note3

I am now! Thanks

ALSO I'm trying not to confuse myself here too! The 88-94 trucks have "less wiring" to mess with than the 95-98 trucks (I think I'm right on my years). When the dash changed and the Vortec engines came into play lots of things changed. The info I am interested in (being my truck is 89) is the for the non-Vortec years. Just trying to clarify a little for the possible searcher here AND I'm 2 wheel drive, no Tech, no cruise control, no manual trans

 

[90W7]

I am now! Thanks

ALSO I'm trying not to confuse myself here too! The 88-94 trucks have "less wiring" to mess with than the 95-98 trucks (I think I'm right on my years). When the dash changed and the Vortec engines came into play lots of things changed. The info I am interested in (being my truck is 89) is the for the non-Vortec years. Just trying to clarify a little for the possible searcher here AND I'm 2 wheel drive, no Tech, no cruise control, no manual trans

Yep you got it right. I fall into the 88-94 category too.

The 94 has the "newer grill"
The 95 has the new rounded dash But still had a tbi motor
And 96+ had the vortec motors.

Sent from my throttle body injected galaxy note3

 

[95SUBURBANLM7]

All right, so I just said heck with it and started connecting wires. I've looked at the schematics and I believe this is right, but can someone that's done this confirm?
Old harness B/E/F > LS Harness B/R
B12 Fuel Pump Signal (16ga) + 9R Fuel Pump Relay Control (18ga)
F8 4WD Low Range Signal + 16R 4WD Low Signal
E6 MIL + 46R MIL
E12 A/C Signal + 55R A/C Low Pressure Switch Signal

Does that look right so far?

EDIT:

Upon further review, I think F6 should go to 9R. If that is true, where do I connect B12? I am looking at the schematics, but I guess Im not as proficient at reading them as I thought I was.

I have more connections that I need to make, Ill list them and if you guys can help me make the connections Ill clean this up and repost it so anyone doing this swap can have an easier go at this sort of swap.

From the old harness, I have this left:

F9 - Serial Data
F13 - VSS
F15 - Ignition Feed
B8 - ECT Signal (I believe this is going to connect to the '95 ECT that screws into the pass side cyl head)
B10 - Cruise Control
B12 - Fuel Pump Signal
E13 - Brake Signal
E15 - Ignition Feed
E16 - Battery Feed

From the LS harness, I have this:

19B - Ignition Feed
20B - Battery Feed
33B - TCC Brake Signal Switch (What the hell is TCC?)
74B - ECT Signal
75B - Ignition Feed (AllData lists this as "Off/Run/Crank Voltage", is it still just the "Ignition Feed" like the rest of the pink wires?)


I have more, but I have to step away for the computer for a moment.

33B -

 

[90W7]

All right, so I just said heck with it and started connecting wires. I've looked at the schematics and I believe this is righ, but can someone that's done this confirm?
Old harness B/E/F > LS Harness B/R
B12+9R (16ga+18ga)
F8+16R
E6+46R
E12+55R

Does that look right so far?

That's Chinese to me. I have no clue what the connectors/pins are. Any pics?

You just need to find 12v switched and 12v always hot sources and wire your ls harness to them.

You must be registered for see images attach

basically the wires in the above picture just find a spot for them in your 95's fuse box.

Or are you trying to wire each circuit in individually?

Sent from my throttle body injected galaxy note3

 

[95SUBURBANLM7]

That's Chinese to me. I have no clue what the connectors/pins are. Any pics?

You just need to find 12v switched and 12v always hot sources and wire your ls harness to them.

You must be registered for see images attach

basically the wires in the above picture just find a spot for them in your 95's fuse box.

Or are you trying to wire each circuit in individually?

Sent from my throttle body injected galaxy note3

You're right, it is Chinese. My bad. What I am listing there is the old ECU pinouts going to what I believe is the relevant pinouts to the LS ECU. The 1995 ECU has two connectors, red and blue. Each of those connectors has a side to it, red has A&B and blue has E&F. So F6 would be on the blue connector, "Fuel Pump Relay Control".

The 2002 LS ECU has two connectors, a blue and a red. Both connectors have eighty pins. So 55R would be pin 55 on the red connector, "A/C Low Pressure Switch Signal". My references for this are a printout from AllData and lt1swap.com.

Yes I am, Im trying to connect the fuel relay, MIL, A/C signal, etc from the old harness to the new harness. Now some of these wires will be going from the LS ECU to the C100 connector, but I havent gotten there yet so I wont bother listing just yet.

I appreciate the reply.