Holley EFI Gen III HEMI Main Harness w/ TPS & IAC: Chrysler 300 / Dodge Ram 1500 (03-15 / 03-10)

Holley EFI Gen III HEMI Main Harness

Gen III HEMI Engines

558-116

Overview:

The Holley EFI Gen III HEMI Main Harness is a precision-engineered wiring solution designed specifically for Gen III HEMI engines equipped with aftermarket cable-actuated throttle bodies. This harness serves as the critical interface between your Holley EFI ECU and the engine, enabling full control over fuel delivery and ignition timing. Ideal for enthusiasts performing engine swaps or power upgrades, it supports advanced tuning capabilities including power adders such as nitrous oxide, superchargers, and turbochargers, as well as compatibility with methanol and water injection systems.

By utilizing most of the stock sensors, this harness simplifies installation while delivering the most advanced fuel and spark control available for Gen III HEMI platforms. It is intended to be used alongside Holley EFI injector and coil harnesses, plus two ignition modules, to create a complete EFI wiring solution.

Key Features:

Designed with performance and reliability in mind, the Holley EFI Gen III HEMI Main Harness offers a range of features that make it the ideal choice for modern EFI conversions and upgrades:

• Complete Gen III HEMI main harness with integrated Idle Air Control (IAC) motor and Throttle Position Sensor (TPS) wiring/connectors
• Enables precise fuel and spark control through Holley EFI for enhanced engine performance
• Supports tuning with power adders including nitrous, superchargers, turbos, and compatible with methanol and water injection
• Designed specifically for Gen III HEMI engines to ensure perfect fit and function
• Utilizes most factory sensors to maintain OEM-like operation and simplify installation
• Includes two optional connectors for CAN-based Holley modules, expanding system integration possibilities
• Constructed with lightweight, high-temperature TXL grade copper wiring for durability and minimal weight
• Factory-style terminations and OEM-grade connectors provide secure, positive connections
• Harness routed through split-loom braid for superior protection and clean appearance

Construction & Design:

The Holley EFI Gen III HEMI Main Harness is built with high-quality TXL grade copper wiring, chosen for its excellent conductivity and resistance to heat. The wiring is sheathed in a high-temperature sleeve and routed through a split-loom braid, offering robust protection against abrasion and environmental damage while maintaining a neat, professional look under the hood. OEM-grade connectors and factory-style terminations ensure a secure, reliable connection that resists corrosion and vibration, critical for maintaining consistent engine management signals.

Every aspect of the harness is engineered to fit the Gen III HEMI engine platform precisely, reducing installation time and minimizing the need for modifications or splicing. This attention to detail guarantees a clean, factory-quality wiring solution that supports advanced EFI functionality.

Installation & Fitment:

This main harness is designed for straightforward installation on Gen III HEMI engines with aftermarket cable-actuated throttle bodies. It is intended to be used in conjunction with Holley EFI injector and coil harnesses, as well as two ignition modules, to complete the EFI wiring system. Most stock sensors are compatible, which helps preserve OEM sensor functionality and reduces the complexity of the installation.

While installation requires basic wiring knowledge and familiarity with EFI systems, the harness’s OEM-style connectors and dedicated wiring paths simplify the process. No major engine modifications are necessary, making this harness an excellent choice for engine swaps, rebuilds, or performance upgrades.

What's Included:

• Holley EFI Gen III HEMI Main Harness with TPS and Idle Air Control connectors
• Two optional CAN-based Holley module connectors
• Split-loom protective braid covering the entire harness

Ideal For:

This harness is perfect for automotive enthusiasts, professional tuners, and engine builders who are upgrading or swapping Gen III HEMI engines and want to leverage the advanced capabilities of Holley EFI. It is especially suited for those adding power adders such as nitrous, superchargers, or turbochargers, or integrating methanol and water injection systems. Whether building a street performance vehicle or a race-ready machine, this harness provides the foundation for precise, reliable engine management.