Painless Wiring Integrated EFI & Chassis Wiring Harness

The Painless Performance Integrated EFI & Chassis Wiring Harness line is the definitive electrical solution for complete vehicle rewires and GM Gen III LS engine swaps. Designed for builders who demand a clean, professional installation, this harness line unifies chassis and fuel injection wiring into a single, fully integrated fuse block — eliminating the complexity and clutter of managing two separate electrical systems.

Rather than piecing together a standalone EFI harness alongside a separate chassis harness, Painless Performance's integrated approach consolidates both into one cohesive unit with a shared multi-circuit fuse block and relay positions. This architecture dramatically simplifies the build process, reduces potential failure points, and delivers a factory-quality result in hot rods, resto-mods, and ground-up custom builds alike.

Key Features:

• Fully integrated design — chassis and EFI wiring share a single fuse block, eliminating redundant fuses and relays across both systems
• GM color-coded chassis connections — familiar OEM wire colors simplify hookup of lighting, HVAC, power accessories, and more
• Clearly labeled EFI connections — printed wire tags on all connectors and open-ended wires eliminate guesswork throughout the installation
• High-grade TXL automotive wire — high strand-count copper conductors and premium insulation deliver superior abrasion resistance, heat tolerance, and long-term reliability
• 100% quality tested — every harness is verified on OmniScanners to confirm complete circuit integrity before it ships
• Comprehensive chassis circuit coverage — supports lighting, charging, starting, instrumentation, power accessories, cooling fans, wipers, cruise control, and more
• Complete EFI engine management integration — covers the ECM, ignition coils, injectors, critical sensors, transmission control, data link connector, and gauge outputs
• Multiple configurations available — mechanical throttle body and electronic throttle-by-wire variants available to match a wide range of engine and transmission combinations
• Firewall passthrough included — grommet-style passthrough keeps the installation neat and weatherproof
• American made — every harness is proudly produced in Fort Worth, TX, backed by Painless Performance's in-house technical support team

Whether dropping a GM Gen III LS engine into a classic car, building a restomod from scratch, or completely rewiring an existing vehicle, the Painless Performance Integrated EFI & Chassis Harness line delivers the coverage, quality, and ease of installation that professional builders and serious enthusiasts rely on. Backed by decades of automotive wiring expertise, each harness in this line is engineered to make complex electrical work straightforward and dependable.