How to make a standalone LS wiring harness
You can build one from the donor harness by stripping it down to the circuits the engine needs. The job is doable but tedious and time-consuming (LSX Magazine). A standalone typically keeps: PCM power and grounds, ignition coils, injectors, crank/cam/knock sensors, MAF/IAT/coolant temperature, O2 sensors, the throttle body (plus the pedal on drive-by-wire), the fuel pump relay, the check-engine light, and transmission circuits if you run an automatic.
Rules that save headaches:
- Keep the harness matched to the reluctor (24x vs 58x) and the throttle type.
- Use proper-gauge wire for high-current circuits (fuel pump, ignition), soldered and heat-shrunk joints, and solid grounds.
- The PCM still needs reprogramming (VATS delete, injector/MAF data, transmission).
If time matters more than money, a prebuilt standalone (about $500+) is the usual route.
Confidence: medium — sources disagree or are limited; check the sources below.
Related questions
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Sources
- Holley's Terminator X Vs. GM Standalone ECU For LS Swaps — LSX Magazine
- LS Swap How-To Guide — Speedway Motors
- What Every LS Swap Builder Needs to Know About the PCM and Harness — PSI Conversion