Wiring a LS1 into a LT1 Car

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11-15-2008, 03:20 PM

the_merv

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Wiring a LS1 into a LT1 Car

LS1 HARNESS INTO LT1 CAR

I decided to make a thread to help those that are looking into this, it seems like this is getting more popular to do.
I don't have all my notes infront of me, so I'm going off of memory, but it'll be close enough to work with..

The biggest thing with all of this is that it's quite easy..all you have to do is properly Power it, Ground it, and match up the right Wires, and you are good.

To start, get ahold of a LS1 Harness that you want to use. Mine was from a 1999 Z28.

This is a list of things that I needed to help me build my Harness:

All Data Printouts of the Connector Pin Diagrams-
Under Dash: C210, C220, C230 Connectors for LT1, C220, C230 Connectors for LS1 Harness
Wheel Well: C100, C105 Connectors for LT1, C100, C101, C105 Connectors for LS1 Harness
LS1 PCM Connector Pin Diagrams
Extra 3-Wire Connector identical to the TPS Sensor Connector
Extra Male Connector of Black 4-Pin Harness Connector (C210) under LT1 Dash
Extra Wire to extend some of the existing Wires
Electrical Tools
Butt Connectors
Electrical Tape
Soldering Tools if you want to do that

To build this Harness some of the Wires in the Connectors have to be taken out and moved around on the Harness to match it properly to the Car to work, and some Connectors have to be added, hence the extra ones above. I re-pinned all the Harness Connectors to match the Car perfectly.

*Throughout this when I say that the Wire has to go to the Dash Connectors or Wheel Well Connectors, that means that you have to line it up and match it to the Wire on the Connectors that the Wire is going to.

HARNESS MODS

I started by stripping down the Harness I got and looking at the Harness and figuring out what wires were what..and there is pretty much everything there that the LT1 has already.

*Here is a quick note: Cruise Control and the Fuel System Wiring in the LT1 Cars are their own independent Systems and do not have to be messed with.* Keep this in mind, most people have a mis-conception about this.

Here is the necessary wiring pretty much once you figure out everything in the Harness:

Starter:
Big Purple Wire that is in the Harness near the Connectors on the Wheel Well. I moved that and extended it to the Connecters under the Dash, and it lines up on the Black 4-Pin Connector(C210). This is why you will need the extra Male C-210 Connector for this.

Fuel Pump Relay Ground:
This is a Black Wire that is on that C210 Connector on the Car. This Wire is in the Harness, and it has to be matched to this one. It sometimes is referred to as the Sender Ground. Put this Wire into the Male C210 Connector with the Starter Wire.

Fuel Pump Relay Power:
This Wire is in the LS1 Harness and it has to be lined up with the Wire in the LT1 Dash Harness. This is the Wire that comes from the PCM that powers the Fuel Pump Relay. For the 1999-2002 LS1 Harness this wire is PCM RED #9, and goes to C101, Pin D.
There is also another wire called Theft Deterrent Fuel Enable, this is for VATS Fuel Control. This one is located in PCM RED #30 in the LS1 Harness, and goes to C230, Pin E in the stock 1999-2002 LS1 Harness. If VATS is disabled, this wire can be removed.

Speedometer, Tachometer, Oil Pressure:
Find these Wires in the Harness and line these up with the ones on the Car.

*The next couple of wiring modifications are for the Gauges and to make the Harness work for the Car's stock Gauge Cluster.
The reason you have to do this and the reason this works is cause the F-bodies that are 1998 and back use Analog Gauges, the 1999 and up use a BCM(Body Control Module) that sends one signal to the Gauges and it breaks it down digitally from there. So on a Harness that is 1999 and up, you have to wire in these extra Wires.

Temp Sensor signal to Gauge(1999 and up LS1 Harness):
Get a 1998 F-body LS1 Temp Sensor(GM Part #12551708) and use the 3-Pin Connector identical to the one that is on the Throttle Position Sensor.

Remove the current Connector and get the extra 3-Wire Connector that is like the TPS Connector. Wire in the bottom Wires(Yellow and Black) on the same sides that they are on, and then the third wire (Pin C) is the wire that goes to your Temp Gauge, run this wire to the Connectors under the Dash. I currently have mine setup like that, and I have no problems, workes perfectly.

Alternator signal to Gauge:
**Definate for a 1999-02 LS1 Fbody Harness: Follow the Red Wire that comes from the Alternator and eventually goes to the PCM Connectors. Splice into this and run the wire to the Connectors under the Dash.
On the 1998 Harnesses it's already in the Harness as C220 Pin A.

OBDII Diagnostic Port Wiring:
My Car is a 1995 Model, it had the OBDII Port in it from the Factory, and it was already wired. I traced the Wires and they were all there from the Factory.
In the LS1 Harness is whats called the Serial Data Wire, it's a Tan or Green Wire, this is the Wire that is for the Diagnostic and Tuning of the PCM. The 1999 and up Cars had 2 of these wires, one was for the PCM, the other was the Wire that went to the Gauges that carried 4 different Gauge Signals. You will need the Tuning one ONLY and can get rid of the other one, the correct Wire is PCM BLUE CONNECTOR, PIN 58. When you find this Wire, it needs to go to the Dash Wires.

This is the proper Pinouts for the 16-Pin OBDII Connector:
Pin 2: Diagnostic Signal Wire, this is the Serial Data Wire from the PCM, match this to the Dash Connectors and with the Harness.
Pin 4: Ground
Pin 5: Ground
Pin 16: Constant Power from Battery

Various Power Wires:
Throughout the Harness there are many Power Wires, all of them are Circuits that need to be powered. On the Wheel Well Connectors are pretty where they all come into the Harness at. They come from the Fuse Box.

I re-built my Fuse Box cause after matching the ones that I could match up, I found that the LS1 Harness has 2 more Circuits that require power than the LT1 Car. Here is how I did it..

PCM Constant(PCM CONST) Power:
This is an Orange Wire in the Wheel Well Connectors or in the Connectors under the Glove Box, this is a Fused Circuit, it's a Constant Power Wire off of the Battery. They go to PCM BLUE #20 & #57.

PCM Ignition(PCM IGN) Power:
This is a Pink Wire that is in the Wheel Well Connectors or in the Connectors under the Glove Box, this is a Power Wire that is on a Fused Circuit coming from the Fuse Box. It goes through the Harness and powers PCM BLUE #19 when the Key is turned on.

Injector(INJ) Power, Bank 1 and 2:
Both of these are Pink Power Wires that are in the Wheel Well Connectors, they are Fused Power Wires that come from the Fuse Box. They also power the Coils. The LT1 car had one circuit for these, the LS1 has two.

MAF, O2's:
This is a Pink Power Wire that is in the LS1 Harness that powers the MAF Sensor and the O2 Sensor Circuits. It is also called ENG SNSR (Engine Sensors).

Transmission:
This is a Pink Power Wire that is in the LS1 Harness that powers the 4L60E Transmission Circuits. I ran this one as a circuit in the Fuse Box aswell. I re-wired this Wire in the Harness to power the Reverse Lockout Solenoid, and the Reverse Light Switch when I converted it over to the T56 setup.
T56 Harness is powered from the MAF/O2 Circuit, Rev Lights are powered on a seperate 12v.

Grounds:
Throughout the Harness there are many Grounds. There is one Ground that is on the Wheel Well Connectors in the LS1 Harness, I traced that and removed it, the grounds that were in the Harness grounded everything that needed to be grounded, this one wasn't necessary.

There are 3 Grounding Wires that bolt behind the Drivers side Head. I relocated these in the Harness to the front of the Passenger side Head when I did my conversion.

All this mentioned here is pretty much the essential stuff to get it running. After I had all this done and everything properly matched, I had a bunch of extra Wires. I kept the necessary things to make the Engine run. Some people may want some of the other little things that are in the Harness, they are not hard to wire, but I took them out to make things easy and simple.

I didn't need any of the Air Conditioning Wiring, the Low Oil Light, Low Coolant Light, Cruise Control Wiring and some extra fuel system wiring. I also took out the AIR, EGR, TCS, Rear O2's, EVAP, and all the extra 5V Refrence Wires that were all over the place. I had a pile of extra Wires when I was done.

To correctly do this, I suggest following every Wire that you want to remove directly to the PCM Connector and finding out what it is first. That is where the PCM Connector Pin Diagrams will help. Some of the Wires will be spliced into other ones in the Harness also, clip them as close as you can and tape up the spot where you clipped them to make sure it's clean.

This swap wasn't that hard to do, just time consuming.

That and if you know what you are looking at and can use what I said here to relate it to what you have..you will see that this is a pretty generic guide to swap a LS into just about anything..I just did it for a LT1-specific F-body swap.
I gave the basics here to get started..as in identified the Powers, Grounds, and the essentials inbetween. If you know how to supply power to a Fuse Box and can integrate that into a Harness..then you can build your own Harness without problems.

Hope this helps..

Last edited by the_merv; 07-10-2014 at 09:59 PM.

Wiring a LS1 into a LT1 Car

Wiring a LS1 into a LT1 Car

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