They are completely plug and play with switched power, constant power and ground connections required. Harnesses allow for installing the PCM underneath the dash of your vehicle with a sliding grommet. STAND ALONE WIRING HARNESS STANDALONE LS1 4L60E FITS 4.8L 5.3L 6.0L 99-03 VORTEC. Wiring Harness W/ 4L60E For 99-03 VORTEC 4.8 5.3 6.0 VORTEC 99-03 Engines Transmissions Leak Proof Plug and Play, Wiring Harnesses with Mechanical Throttle Body and 4L60E LS1 Transmissions. High Quality, Economical, Complete Standalone Wiring Harnesses.They Are Completely Plug And Play With Switched Power, Constant Power And Ground Connections Required. Harnesses Allow For Installing The PCM Underneath The Dash Of Your Vehicle With A Sliding Grommet Seal For That Professional Leak Proof Look. Note That Harnesses Are For Non-Emissions Equipped Vehicles And Do Not Include Air Pump Or EGR Provisions. 99 -'03 Vortec 4.8, 5.3, 6.0 Engines with Mechanical Throttle Body and 4L60E Transmissions. Complete Engine and Transmission Wiring Harness. Including all engine and transmission sensor connectors, ALDL Connector, 7 ATO Style Fuse Block, Fuel Pump Relay, Switched Power Ignition Relay, Cruise Control Wiring, Performance Shift Mode Wiring, MIL Light Wiring, P/N Wiring, TCC/Switch Wiring, Tach Wiring. These harnesses are designed for'99 -'03 Vortec retrofits into older muscle cars and street rods or newer non-emissions controlled vehicles. Harnesses allow for installing the PCM underneath the dash of your vehicle with a sliding grommet seal for that professional leak proof look. Harnesses are professionally constructed from Brand New GMDelphi Connectors and TXL (Polyethylene Cross Linked) High Temperature Wire to GM Specifications. Feedback is very important to us. It is impossible to address issues if we do not know about them! Faction is our ultimate goal. We work hard to earn your trust and future business. A If you receive a defective item, you may return it or ask for a discount. Due to time zones, our reply to your questions may not be immediately. If it's non-workdays, please kindly be patient and wait till Monday. The item "STAND ALONE WIRING HARNESS STANDALONE LS1 4L60E FITS 4.8L 5.3L 6.0L 99-03 VORTEC" is in sale since Wednesday, April 21, 2021. This item is in the category "eBay Motors\Parts & Accessories\Car & Truck Parts\Air Intake & Fuel Delivery\Fuel Inject. The seller is "zhuliyun-3" and is located in Monroe Township, New Jersey. This item can be shipped to United States.