GENERAL INSTALLATION TROUBLESHOOTING
Below is a comprehensive list of the frequently asked questions we receive via our email contact form.

WHERE DOES THE SINGLE RED WIRE COMING FROM RELAY BLOCK GO?
•    The red wire provides switched power signal for the PCM. Connect to a 12 volt source that has power with the key ‘ON’ AND WHEN ‘CRANKING. Note that in older GM Vehicles, the ignition wire in the engine compartment (White cloth covered) is not a 12-volt source. The most common spot to find this type of power is in the factory chassis fuse box. It is typically marked as ‘IGN’ power NOT ‘ACC’ power.  
Ignition Power Wiring

WHERE DO THE TWO RING TERMINALS AT THE STARTER GET CONNECTED TO?
•    The 2 black wires with the large ring terminals provide all the power to the harness. They get connected to the large stud on the starter, which should have battery power.
Constant Power Wiring

WHY DON’T MY OXYGEN SENSORS PLUG IN?

•    PSI harnesses are designed to use the most popular Oxygen sensor applications. For peak engine performance, PSI recommends the oxygen sensors be replaced, especially if vehicle/engine history is unknown.  New Delphi Oxygen sensors can be purchased from PSI, or Table 2 of your harness instructions will provide GM part numbers for the correct sensor.

WHERE SHOULD I INSTALL MY OXYGEN SENSORS IF I HAVE LONG TUBE HEADERS?
•    O2 sensors should always be installed as close to the engine as possible in order to allow for proper sensor heating and function. The further from the engine the sensors are installed the more time the sensors will take to heat up and put the engine in closed loop.

HOW DO I HOOK UP MY AC REQUEST WIRE?

•    The AC Request Wire must be hooked up to a 12-volt source when the ac compressor clutch is engaged.

WHERE DO I PLUG IN THE PURPLE AND YELLOW WIRES.
•    This varies depending on your specific Harness.  Please check your wiring harness instruction manual - Instructions

WHAT DO I DO WITH ORANGE WIRE?
•    Run to ground (IN PARK AND NEUTRAL). It is not a neutral safety wire and will not prevent the engine from starting. Hooking this wire up is ‘Optional’.

DO I NEED TO HOOK UP MY OIL PRESSURE CONNECTOR?
•    Oil pressure wiring only needs to be hooked up if you are using Variable Valve Timing (VVT). This function is only present on Gen IV (58X) engine applications. For all other applications the engine oil pressure wiring is not required to make the engine function properly. When using an aftermarket oil pressure gage, you must use the sender that came with the gage and wire it directly.

WHERE CAN I INSTALL MY COOLANT TEMPERATURE GAUGE SENDER?
•    When using an aftermarket water temperature gage, the sender that came with the gage must be used and wired directly to the gauge. Most aftermarket gauges use senders with standard US threads. However, LS engines have metric threads, therefore a fitting must be used to adapt the threads. The port on the rear of the passenger cylinder head is most commonly used for this function. These adapters are available through PSI.
Coolant Temperature Gauge Sender

HOW DO I WIRE UP MY FUEL PUMP?
•    Using Figure 2 and specific connections indicated in Table 4, connect the wiring as directed. All connections in table 4 are required unless otherwise noted.

HOW DO I WIRE UP MY SPEEDOMETER?
•    Connect our black "under dash" wire to speedometer. NOTE: Do not tap into VSS wiring in the harness as this can result in the transmission NOT shifting due to a split VSS signal. Following installation, ensure proper calibration of the speedometer per the manufacturer’s instructions.

HOW DO I GET MY AUTO-METER TACHOMETER TO WORK?

•    Connect our white “under dash” wire to their green wire of your tachometer. Note that most aftermarket tachometers work with a 12-volt signal. However, LS controllers use a 5-volt signal which is not directly compatible with most aftermarket tachometers. In these cases a resistor must be wired into the tachometer signal wire. This wiring diagram is located in the PSI instructions which came with your harness.  

NO SIGNAL TO THE TACH AND SPEEDO GAUGE(S)?

•    Most aftermarket tachometers work with a 12-volt signal. However, LS controllers use a 5-volt signal which is not directly compatible with most aftermarket tachometers. In these cases a resistor must be wired into the tachometer signal wire. This wiring diagram is located in the PSI instructions which came with your harness.

VEHICLE RUNS PERFECT BUT NO 5V SIGNAL AT TACH WIRE (GAUGES)?
•    Check that gauge is installed correctly.
•    Contact PSI Tech Support to determing if PCM 'Tach Resolution' is set correctly.

I HAVE A TH350/MANUAL TRANS. DO I NEED TO PLUG IN THE VSS?
•    The VSS is not required, however, it is recommended. In some instances, if the VSS is not hooked up, the PCM will not know how fast the vehicle is going and therefore under hard stopping conditions could abruptly hunt for idle or stall. This condition can be alleviated by installing a VSS or through a local tuner once the swap is completed.

CAN I EXTEND MY MAF CONNECTOR WIRING?
•    Yes you can extend the MAF connector using a properly made extension harness. These are available through PSI in varying lengths to fit many different configurations.

CAN I EXTEND MY OXYGEN SENSOR WIRING?
•    Yes you can extend the oxygen sensor connector using a properly made extension harness. These are available through PSI in varying lengths to fit many different configurations.

CAN I TAP INTO THE VEHICLE SPEED SENSOR (VSS) WIRING PROVIDED WITH MY HARNESS SO MY SPEEDOMETER WILL WORK?
•    No, at no time should you tap into any of the engine sensor wiring supplied with your PSI harness. You speedometer should be wired per the manufacturer’s instructions. This typically requires that you connect the speedometer to the output wire supplied with the PSI wiring harness ‘under dash wiring’ section.  

CAN I TAP INTO THE COOLANT TEMPERATURE SENSOR WIRING PROVIDED WITH MY HARNESS SO MY COOLANT TEMPERATURE GAUGE WILL WORK?
•    No, at no time should you tap into any of the engine sensor wiring supplied with your PSI harness. You temperature gauge should be wired per the manufacturer’s instructions. This typically requires the sender that came with the gauge to be used.

HOW DO I ENSURE THAT MY COIL SUB-ASSEMBLY WIRING HARNESS IS ON THE CORRECT SIDE?

•    When using PSI coil sub-harnesses it is critical that they are oriented correctly. An easy way to check orientation is to confirm the wire color in position 'C' of each coil connector. The colors and corresponding cylinders are as follows:
Coil Sub-Harness Wiring Orientation

HOW DO I MOUNT MY EXTERNAL FUEL PUMP TO MY VEHICLE?

•    The external fuel pumps require insolated mounting brackets to ensure proper, long lasting performance. Most customers will fabricate mounts based on their application or use rubber insulated clamps to secure the pump.
•    If using a Walbro external fuel pump, a mounting kit is available through PSI.
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