Best LS swap wiring harness
Buy a quality standalone harness matched to your engine. A standalone keeps only the circuits the engine needs and removes the donor's body wiring.
Match it to your engine:
- Crank reluctor: 24x (Gen III: LS1, LS6, LQ4, LQ9, 1999–2006 Vortec trucks) or 58x (Gen IV: LS2, LS3, LS7, L76, L92, 2007+ trucks). The harness, PCM and sensors must all match.
- Throttle: drive-by-cable or drive-by-wire. All Gen IV engines are drive-by-wire.
- Transmission: automatic (4L60E/4L80E control) or manual.
Quality matters: very cheap (~$150) harnesses with thin wire and knockoff connectors are a common cause of intermittent misfires and no-starts. Look for TXL high-temperature wire, new Delphi connectors, and circuit testing (PSI Conversion). Typical prices: about $500+ for a quality standalone for a stock PCM; about $1,100 for a ready-to-run kit with a flashed PCM (PSI).
Whatever harness you choose, the PCM still needs a tune (VATS off, injector and MAF data, transmission settings).
Related questions
- Stock PCM vs Holley Terminator X for an LS swap
- How do I tune an LS swap? (HP Tuners basics)
- How to make a standalone LS wiring harness
- VATS delete: what it is and how to do it
- Drive-by-wire vs cable throttle for an LS swap
- Why does my 6.0L LS swap crank but not start?
Sources
- Holley's Terminator X Vs. GM Standalone ECU For LS Swaps — LSX Magazine
- PSI - S10 Sonoma LS Swap Parts — PSI Conversion
- What Every LS Swap Builder Needs to Know About the PCM and Harness — PSI Conversion
- The Complete LS Swap Wiring Harness Buyer's Guide — PSI Conversion