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HAR-G3CA/G3CM

Tools Required for Installation:

  1. Terminal Crimping Tool
  2. Wire Strippers
  3. Electric Drill
  4. 2" Hole saw (for the rubber grommet in the firewall)

CAUTION: BEFORE BEGINNING INSTALLATION, DISCONNECT THE POWER FROM YOUR VEHICLE BY REMOVING THE NEGATIVE BATTERY CABLE FROM THE BATTERY.

TCM-1001

1. PCM/Fuse block mounting:

    PSI harnesses are generally designed to place the computer and fuse block under the passenger side of the dash or kick panel, however anywhere under the dash should work as well. Some applications may allow the computer to reach under the seat, and others have left the computer and fuse block in the engine bay. Make sure water and road debris will not come in direct contact with them. A good exercise is to lay out the wire harness on the floor beside your vehicle and identify all the connectors and wires. Allow enough slack in the harness at places where movement could possibly occur (body to frame, frame to engine, etc.).

    2. Grounding:

      As with all automotive wiring, the grounding circuit is critical for proper operation. Ensure that there is secure grounding of the following, battery to engine, battery to chassis, engine to chassis, harness to engine, and harness to chassis. A ground strap kit KIT-1025 is available from PSI.

      NOTE: This harness is equipped with Ground Wiring on the rear portion of the driver side cylinder head.

                 2a. Connect a ground strap/cable (minimum of a 4 Ga. wire) from the negative battery terminal to the block.

                 2b. Connect a ground strap (minimum of a 4 Ga. wire) from the engine to the chassis (frame).

                 2c. Connect a ground strap from the engine to the body/firewall.

      ENSURE ALL GROUND LOCATIONS ARE CLEANED OF PAINT, GREASE, OIL OR OTHER CONTAMINANTS

      3. Mark the position where the wiring harness will come through the firewall with a metal punch. Using a 2” hole saw, drill a hole in the firewall. Make sure to debur the hole with a file.

      4. From inside the vehicle, feed the Engine Section of the wiring harness through the 2” hole. Push the grommet (already installed on the harness) into the hole until it is seated.

      5. Route the engine compartment section to the top of the engine. The engine section is designed to be separated into left side (driver) and right side (passenger) sections, in much the same way as factory wiring. The driver side of the engine section has the connectors for the IAC, TPS, MAF, and MAP Sensor, reference the engine layout diagram.

      6. Underdash section & gauge connections:

        The wires in this section consist of the DLC, Ignition Feed, MIL indicator, Speedometer Signal, Tachometer, Primary Cooling Fan, Secondary Cooling Fan, Park/Neutral Signal, and Brake Signal wires. These connections are shown in the ‘Under Dash Bundle’ wiring on the next page.

        Optional add-on wires:

        6a. AC Recognition: White wire at pin 18 on the C2 (red) PCM connector.

        • White (18): 12 volts to this wire when the AC compressor receives 12 volts.
        • This wire will command the PCM to increase the idle on the engine to prevent the engine from stalling out due to the extra load of the AC compressor.

        6b. Cruise Control: White wire at pin 13 and green wire at pin 37 on the C2 (red) connector.

        • White (13): Cruise engaged signal.
        • Green (37): Cruise inhibit signal.

        6c. 4WD Signal: Grey wire at pin 16 on the C2 (red or green) connector.

        • Grey (16): Ground wire when in 4WD LOW.
        • This will adjust shift points and speedometer reading when in 4WD low.

        6d. Flex Fuel Signal: White wire at pin 56 on the C1 (blue) connector.

        • White (56): Signal input on a GM flex fuel sensor.

        BROWN Check Engine Light (CEL):

        CEL signal from the PCM is a GROUND signal wire. This wire will ground an automotive light bulb when a check engine light code is sent. The other side of the light bulb will need to be wired to a fused 12 volt source.

        NOTE: If you are using an LED light bulb, a resistor must be added.

        BLACK Speedometer:

        The speedometer output is a 4000 pulse per mile signal which is readable by most aftermarket speedometers. Always refer to your speedometer manufacturer for more information.

        WHITE Tachometer:

        If your aftermarket tachometer has the option, set it to 4 cylinder mode. Many factory GM tachometers will need a 'pull-up' resistor added. The resistor size can vary, however a 1/4 watt, 1000 OHM resistor will often work. This resistor will be added to one end of the tachometer signal wire, and a fused 12 volt key source on the other end.

        Cooling Fan Signal:

        DARK GREEN = Fan 1 (195°)

        DARK BLUE = Fan 2 (205°)

        Each fan trigger is a GROUND trigger. Each fan will need its OWN relay to power the fan. These trigger wires must ground a relay, that will then send power to each fan. PSI offers a dual fan relay kit (KIT-1011) that is pre-wired and only needs connected to your fans and 12 volt sources.

        PURPLE TCC (torque converter clutch) Signal:

        The TCC signal wire is required for any 4L60e or 4L80e application. The purple wire must be connected to a brake switch that will send a constant 12 volt signal to that wire when the brakes are NOT on, and will then send a ground (0 volts) signal when the brake pedal is pressed. Most older vehicles, including any vehicle that did not have an electronic automatic transmission will need to add a two position brake switch kit (KIT-1002). This will allow you to hook up the correct signal for the torque converter to lock and unlock, as well as provide provisions for your factory brake light wiring.

        ORANGE Park / Neutral Signal:

        The connection is NOT required and often ignored. This connection will let the PCM know when you are in park or neutral to accomodate for appropriate timing tables. The wire must be connected IF a crankshaft relearn procedure is required as well.

        NOTE: This wire IS NOT a neutral safety.

        Additional gauge connections:

        Oil Pressure: Gen 3 LS computers do not have an oil pressure gauge output wire. This is why there is no oil pressure connector on the harness. You can remove the original LS oil pressure sensor from the engine and replace the sensor with the correct pressure sensor for the gauge you are using. If you are using a factory gauge cluster in your vehicle, you will use the factory oil pressure sensor for that vehicle.

        Engine Coolant Temp: There is also no coolant temp output signal from LS computers. Similar to the oil pressure, you will have to add the coolant temp sensor that corresponds to the gauge you are using. You must retain the factory LS coolant temp sensor in the driver side cylinder head. A secondary sensor can be added to the rear of the passenger cylinder head.

        NOTE: PSI offers a gauge install kit (KIT-1027) that includes a coolant temp adapter (12mm x 1.5 to 1⁄8 NPT) and oil pressure adapter (16mm x 1.5 to 1⁄8 NPT) for standard 1/8th sensors. KIT-1027 also includes a 1k ohm ¼ watt resistor required for many tachometers.

        Dakota Digital Gauges

        If using a cluster from Dakota Digital, the BIM module can be used to simplify installation. The BIM-01-2 module will allow all parameters read by the PCM to be sent directly to the gauge cluster with one plug. The BIM module will plug into the OBD2 data port on the PSI harness and will come with a cable to connect the the Dakota cluster. On a gen 3 LS system, you will have to add the oil pressure sensor (included with Dakota Digital kits) and run a wire from the oil pressure sensor directly to the input box for Dakota clusters as oil pressure is not read by the PCM. 

        7. Ignition Feed

        A red Ignition Feed wire is coiled up at the fuse block. This wire must be connected to a power source on the vehicles fuse block that provided 12V Key on And Cranking Power. A common source is the “ACC” location on a GM fuse block or a distributor coil wire.

        8. Fuel Pump Wiring

        A fuel pump relay is provided with the signal side of the relay being pre-wired from PSI. However, in order to provide a clean installation, the feed and output sides of the relay are not wired. PSI has provided you with two blade terminals to complete this circuit. Ensure that properly sized and fused wiring is used, depending on the capacity of your fuel pump. Measure the length of wire needed to reach the fuel pump, strip the wire and crimp the supplied blade terminal onto the wire. Insert the terminal into the relay holder. Perform the same operation for wiring the power supply side of the relay ensuring that the wire is run from an appropriate power source.

        CAUTION: BE SURE TO PROPERLY GROUND AND FUSE YOUR FUEL PUMP OR ENGINE DAMAGE MAY OCCUR!

        9. Connect the PCM connectors to the PCM, BEING CAREFUL NOT TO BEND ANY PINS. Connectors are color coded to prevent incorrect installation.

          CAUTION: BE SURE THE IGNITION IS OFF WHEN YOU RECONNECT THE BATTERY OR DAMAGE TO THE PCM WILL OCCUR

          10. The fuel pump should prime for a few seconds with the initial key turn to accessory power position. If fuel is being run through the system for the first time, ensure you have no fuel leaks at any fittings, the fuel rails, or the injectors. Note: the fuel pump will not prime on every key turn!

          11. Time to start the engine!

            If you have ensured you have no fuel, oil, or water leaks and the battery is properly charged, it is time to turn the key and crank the engine over. Any stock engine should fire over and run well with a properly tuned computer. If the engine is modified (specifically with an aftermarket camshaft), the engine should still run but it will need custom tuning to run properly. It is not recommended to drive the vehicle if you have an aggressive aftermarket camshaft.