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Air and Fuel› Throttle Cables, Linkages, Brackets and Components

PSI Conversion

Standalone EFI Wiring Harness

Name: Standalone EFI Wiring Harness
Brand: PSI Conversion
SKU: HAR-G3WA

$581.03

SKU: HAR-G3WA

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$100 Minimum Order

Non-Returnable Item

DIY PRO SHOP

Moderate — 2–4 hours

Overview

The PSI HAR-G3WA is a standalone wiring harness designed for retrofitting 2003-2007 Gen 3 LS/Vortec engines with drive-by-wire systems and 4L60E-75/4L80E transmissions. It allows for the use of factory intake manifolds and various injector types, including EV1, Multec, and EV6/USCAR. The harness features a four-wire hookup for essential engine and transmission operation, making it suitable for older muscle cars, street rods, or non-emissions controlled vehicles.

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The PSI Conversion HAR-G3WA is a standalone wiring harness engineered for retrofitting 2003-2007 Chevrolet, GMC, Cadillac, and Hummer 4.8L, 5.3L, 6.0L, and 5.7L Vortec engines into street rods, muscle cars, or non-emissions controlled vehicles. This harness is specifically designed for drive-by-wire configurations and supports 4L60E, 4L65E, and 4L80E automatic transmissions, providing a simplified solution for complex engine swaps. It is designed to allow the PCM to be mounted inside the vehicle, typically in the glove compartment area, with approximately 4.5 feet of length provided from the rear of the cylinder head. Installation requires basic four-wire hookups for switched power, constant power, and ground connections. Note that all harnesses require PCM VATs removal, which is available through PSI. If opting for the E85 flex-fuel signal wire, custom tuning is required. Additional functionality can be integrated through optional upgrades, such as 4WD signal wires for adjusting shift points in low-range, and cruise control support. Proper operation relies on the use of a compatible green/blue 242 PCM, and fan relay kits (KIT-1010) are sold separately.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

Brand	PSI Conversion
Part Number	HAR-G3WA
Category	Air and Fuel

Videos

PSI How to: Choose the Right Pedal for Your LT / LSX Swap ( Drive By Wire)

PSI How to Wire Fans for an LS or LT Swap Kit-1010 kit-1010 KIT-1010

PSI Conversion Your One Stop Shop for all Things LT / LS Swaps Commercial

PSI How To: Which PCM should I use on my LS / LT Swap ( BONUS: PCM Reference Guide at end)

HOW TO WIRE A PSI STAND ALONE LS HARNESS! (70CHEVELLE) LSX

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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