58x LS2, LS3, LS7 Stand Alone Engine Harness For E38 ECU Built From Scratch Stand Alone Engine Harness. An engine management harness is pretty much what you will find from most wiring harness companies. Basically, it contains all of the necessary functions to make the engine start and run, while also supplying any necessary signals from the computer such as speedometer and tachometer. Standalone LS2 / LS3 Swap Wiring Harness | Drive by Cable Brand new Standalone LS2 / LS3 swap (drive by cable) wiring harness. No cores or modifications needed. Made in USA with a start-up guarantee.