The LS1 harness basically connects to the rest of the car thru a few specific connectors. The first four are located close together in the area of right shock tower...
...C100...black 10 pin connector.
............A- pink (bank 1 ign/inj switched 12v 15amp power in)
............G- pink (transmission/EVAP switched 12v 15amp power in)
............J- dk green (cooling fan 1 relay control out)
...C101...grey 10 pin connector.
............B- pink (bank 2 ign/inj switched 12v 15amp power in)
............D- dk green w/ white stripe (fuel pump relay control out)
............E- pink w/ black stripe (switched 12v 15amp power for PCM in)
............G- orange (constant power for PCM 12v 50amp power in)
............H- black w/ white stripe (ground in)
...C102...
............A- purple (starter solenoid "start" power in)
...C105...black 8 pin connector.
............B- pink (trans/stop lamp/heated o2/MAF 12v 20amp power in)
............G- white (tach signal out)

The other two are located close together behind the firewall, inside the passenger compartment, on the other side of the firewall grommet.
...C220...natural color 10 pin connector.
............E- black w/ white stripe (ground in)
............G- brown (back-up lite switch switched 12v power in)
............H- lt green (back-up lite switch out to lites)
............K- dk green w/ white stripe (VSS signal 4000ppm out)
...C230...blue 10 pin connector.
............B- brown (MIL "malfunction indicator lamp" feed)
............E- dark blue (VATS fuel enable input)
............K- dk green (serial data class 2 out OBD-II connector)

The only other two points that the LS1 harness needs connected are down by the LS1's starter...
...purple wire... needs to be connected to the starter solenoid's "S" terminal.
...open ground lug... needs to be connected to a block ground.

The GM color code for wiring is very consistant. When in doubt, the following applies to any loose ends you might end up with in connectors C100, C101, C105, C220, and C230...
...red wires...all loose red wires should be connected to "12v+" protected by a fusible link.
...orange wires...all loose orange wires should be connected to "12v+" protected by a fuse of at least 10a.
...pink wires...all these wires in the LS1 harness should connect to a 12v "switched +" power source hot in "start" and "run".
...black...all these wires in the LS1 harness should connect to ground.
...black w/ white stripe...all these wires in the LS1 harness should connect to ground.

In the text below, the connector ID numbers are listed first are for '86-'87 harnesses. The 2nd ID numbers listed in brackets ( ) is the connector ID number for the '88-'91 harnesses. EXAMPLE- X-04(FE-02)...X-04 is the connector ID number for the '86-'87 harnesses, (FE-02) is the connector ID number for the '88-'91 harnesses.

The following set of connections take place mainly between the LS1's C100/C101/C102/C105 connectors and the Rx-7's X-16 connector, so much so that an 8 wire connecting harness could be made if one had the correct connectors to build it with. A little bit of caution is necessary when dealing with the black w/ white stripe wires in the RX-7's X-16 connector, as the two that are side-by-side are "hot in run & start", and the one by itself near the missing center terminal is "hot in start only". The connections are as follows...
LS1 C100...
.........pink- connect to RX-7 connector X-16's black w/ white stripe "hot in run & start" wire
.........pink- connect to RX-7 connector X-16's black w/ yellow stripe wire
LS1 C101...
.........pink- connect to RX-7 connector X-16's black w/ yellow stripe wire
.........dk green w/ white stripe- connect to RX-7 connector X-16's brown wire
.........pink w/ black stripe- connect to RX-7 connector X-16's black w/ white stripe "hot in start & run" wire
.........orange- connect to RX-7 connector X-16's blue w/ red stripe wire
LS1 C102...
.........purple- connect to RX-7 connector X-16's black w/ red stripe "hot in start only" wire
LS1 C105...
.........pink- connect to RX-7 connector X-16's black w/ white stripe "hot in start & run" wire
.........white- (connection listed below in "tachometer signal wiring" section)

Re-connecting The Battery To The RX-7's Harness...when the rotary?s engine harness is removed from the car, a vital wire is lost that runs from the 80A fuse in the main fuse box to the large stud on the back of the RX-7?s alternator, and also to the ignition switch through connector X-23 (a large single terminal connector located between the main fuse block and the driver?s strut tower). This wire was originally black, and very thick, appx. 10ga. Be sure to replace it with wire of at least the same capacity, that connects all three points in the circuit, including the large stud on the back of the LS1 alternator.

Neutral Safety Switch...
...NA manual cars...LS1 equipped w/ 4L60E trans- Route a wire from RX-7's connector X-08(FE-05) black w/ white stripe "hot in start only" wire (next to the missing center terminal), thru the neutral safety switch, and back to RX-7's connector X-08(FE-05) black w/ red stripe wire. For LS1 equipped w/ T-56 manual trans- just connect the two terminals with a wire loop, as a neutral safety switch is not needed.
...NA automatic cars...If you are keeping your automatic car automatic, you need to route your purple wire in LS1 connector C102 thru a neutral safety switch.
...Turbo-II cars...On T-II cars, connector X-08 is a simple round 1 wire connector. If you kept a manual trans in your T-II, nothing needs to plug in here. If you installed an automatic in your T-II, you need to route your purple wire in LS1 connector C102 thru a neutral safety switch

Locating & Re-wiring The RX-7's Fuel Pump Control Relay(s)...Mazda calls the main fuel pump relay the "Circuit Opening Relay", a square relay with a 6 terminal connector Ba-01(F-08) (2 rows of 3), which is located under the steering column. For the non-turbo models, this is the only fuel pump control relay. The Turbo II models used an additional relay called the "Fuel Pump Relay & Resistor", located in front of the passenger side strut tower under the stock air cleaner, using a round connector (F-09) with 6 terminals (2 rows of 3). The wiring modifications are as follows...
...ALL Models-...The RX-7 circuit opening relay's Ba-01 connector is a retangular 6 pin connector located below the RX-7's steering column. Perform the following modification steps 1, 2, and 3 to the wires/pins in the connector (step 4 is performed at RX-7 connector X-16)...
......STEP 1- remove the black w/ white stripe wire from the connector's center pin (opposite the blank hole). This wire will not be used, but it needs to be insulated from the others (as well as from the other wires) and taped back out of the way.
......STEP 2- remove the brown wire/pin from the connector and re-insert this wire into the upper center hole (spot formerly occupied by the black w/ white stripe wire we removed in step 1)
......STEP 3- remove the black wire/pin from the connector and re-insert this wire into the lower right spot to the left of the open hole (spot formerly occupied by the brown wire).
......STEP 4- connect the brown wire in the RX-7's X-16 connector to the LS1 C101 connector's terminal "D" dk green w/ white stripe wire.
These modifications allow the LS1's PCM to control the RX-7's Circuit Opening Relay as a fuel pump relay.
...Turbo II Only-...On the turbo models, there is also the "fuel pump relay and resistor". It's function was to provide extra fuel pressure under boost conditions by closing an internal set of contacts to effectively bypass a voltage dropping resistor. When installing a LS1, we bypass this entirely by connecting RX-7 connector Ba-01's blue wire w/ red stripe wire directly to the RX-7 connector X-13's blue wires (both blue wires are connected inside the harness - Mazda used 2 parallel blue wires thru the connector to reduce connection resistance). These blue wires power the RX-7's fuel pump.

Temp Sender Location & Installation...The RX-7's rotary engine's temperature sending unit for the dash gauge is a very small single terminal device located below the rotary engine's oil filter. It can be removed from the rotary and installed in your V-8' cylinder head (in back of rear exhaust port on passenger side) using a special reducing bushing. After installation, the sending unit should be connected to the yellow w/ black stripe wire in connector X-16 (non-turbo) or X-15 (turbo). The original connector for the sending unit, C-04(EM-33), can be salvaged from the discarded emissions harness and re-used here for a factory quality connection.

Oil Pressure Sending Unit Wiring... The rotary engine's oil pressure sending unit for the dash gauge is a large round single terminal device located below the rotary engine's oil filter. It can be removed from the rotary and installed in a drilled and tapped hole (1/8" npt) in the small removable cover located just above the LS1's oil filter (retained by 2 bolts w/ 10mm heads) using two 1/8" pipe thread 90 degree elebow fittings (male threads for the block, female threads for the sender) to angle the sender away from the exhaust. A single wrap of the threads with teflon tape should ensure leak free operation. After installation, the sending unit should be connected to the yellow w/ red stripe wire in connector X-04(FE-02). The original connector for the sending unit, C-05(E-10), can be salvaged from the discarded emissions harness and re-used here for a factory quality connection.

LS1/Delco Alternator Wiring...The LS1 alternator output is triggered by a low voltage signal from the LS1 PCM's C-2 "red" connector, pin 15. This wire is contained within the stock LS1's engine harness. The '99-newer LS1 had proper control of the voltage regulator incorporated into the PCM. The '98 LS1 PCM did not, and the circuit needs modification to prevent alternator damage. For proper operation, alternator terminal "L" (red wire) needs to be connected to PCM red C-2 connector's pin 15 thru a 470 ohm resistor. Simply snip the red wire at a conveinant location, and solder the resistor in series with the wire.

Tachometer Signal Wiring...The RX-7's tachometer originally got it's signal from the rotary engine's ECU. The stock rotary engine put out a tach signal that was the same rate as a 4 cyl piston engine. The LS1's PCM puts out a 1/2 rate tach signal for a V-8. Simply using the LS1's tach signal to drive the RX-7 tach will result in a correct reading tach. Connect the LS1 C105's white wire ("PCM tach signal output") to the RX-7's Ba-07 connector's yellow w/ blue stripe wire (formerly the signal input point for the RX-7's tach).

Back-up Lite Switch...To operate the RX-7's back-up lites, Mazda used a transmission mounted SPST switch to complete the circuit. When the RX-7's engine harness is removed with the rotary engine, part of this circuit is removed as well. To restore this circuit, a harness extension will need to be added at connector X-04(FE-02), a rectangular 6 pole connector (2 rows of 3) located under the hood on the driver's side of the brake master cylinder. 2 of the wires in this connector are for the back-up lite switch. These wires are...
...black wire w/ yellow stripe- comes from 7.5a fuse in underdash fusebox. Connect this wire to the LS1 C220 connector's brown wire.
...red wire w/ green stripe- goes to back-up lites. Connect this wire to the LS1 C220 connector's lite green wire.

T-56 "Skip Shift" feature elimination..."skip shift" is an annoying feature GM came up with for the 6spd cars that essentially forces you to "skip" gears under certain conditions in an attempt to improve fuel economy. If you simply unplug the solenoid connector, the LS1 PCM will throw a "DTC P0803" code, which will result in triggering the "MIL" lite. This function can be easily eliminated by simply installing a 2.2k ohm resistor across the wires that formerly went to the skip shift solenoid, located on the driver's side upper part of the T-56's main case. Colors for the 2 wires in this connector are...
......grey...
......pink...
We recommend unplugging and cutting off the harness connector for the solenoid, and simply soldering the 2.2k resistor across the cut wires extending from the harness. Be sure to insulate your work with either tape or, as we prefer, shrink tube.

Low Coolant Level Warning Buzzer and Lite...the original sensor for this circuit was located in the RX-7's top radiator tank. If you do not want to go to the trouble to keep this part of the warning system intact, you can either dis-able the buzzer (located on the outside/bottom of the dash pod), or, simply locate the brown wire that formerly went to the coolant level sensor and connect it to ground. If you need help locating this wire, it is part of the front harness, a single wire leg that comes out of the front harness just in back of the passenger side headlite.

AC System- Relay, Compressor & Pressure Switch...Only 2 circuits need modification for your AC system to function properly.
...AC main relay (G-08)... in the #2 position in the relay rack located in the nose of the car just ahead of the hood latch. It has a square connector with 4 wires attached. It's terminals need to be re-connected as follows...
......blue w/ white stripe wire...connect this wire to one leg of the RX-7's pressure switch located near the RX-7's reciever/drier. The other leg of the pressure switch connects to "12v +" thru the "AC ON" switch.
......red w/ yellow stripe wire...connect this wire to ground.
......black w/ white stripe wire...connect this wire to the "+" side of your compressor's magnetic clutch. Connect the other leg of the magnetic clutch coil goes to ground.
......blue w/ black stripe wire...connect this wire to a "12v ign on" power source.
...AC pressure switch...a 2 terminal switch located next to the RX-7's reciever/drier. The switch's harness connector can be clipped from the front harness and re-used. The 2 legs of this switch/connector can re-wired as follows...
......blue wire...DO NOT CHANGE- oem wire connects to "12v +" thru the "AC ON" switch.
......blue w/ orange stripe wire...connect to the AC Relay's blue w/ black stripe terminal.

OBD II Connector...this under-dash connector is not necessary to run your car, but it will be necessary to access the PCM's diagnostic features and will be required to pass a smog inspection. The OBD II connector was not part of the LS1's engine harness, but can be easily obtained from most '98 or newer cars in a wrecking yard. Simply attach the OBD II connector body under your RX-7's dash in an accessable but inconspicous place, then make the connections listed below. This 16 pin connector is arranged in 2 horizontal rows of eight, with the top row numbered left to right 1 thru 8, and the bottom row numbered 9 thru 16. The necessary connections are listed below...
...pin 2 (purple wire)- class 2 serial data. Connect to LS1 harness connector C230 pin "K" (dk green wire)
...pin 4 (black wire)- connect to chassis ground
...pin 5 (black w/ white stripe wire)- connect to engine ground
...pin 16 (orange wire)- connect to battery "12v+" constant power source.
The rest of the OBD II connector's terminals are not used.

Malfunction Indicator Lamp...this connector is not necessary to run your car, but will be required to pass a smog inspection. Most any 12v lamp will do, and many styles are available from any electronics supply store that can be easily installed in your RX-7. Connections to the "MIL" lamp are as follows...
...lamp leg 1- connect to a switched "12v+" ignition power source.
...lamp leg 2- connect to LS1 connector C-230 pin "B" (brown w/ white stripe wire).