Holley Terminator EFI Input/Output Kit by Holley

Price: 56.25 USD
Availability: InStock

Add extra functionality to your Holley Terminator EFI system with this Terminator EFI input/output wiring kit.

Item #HLY-558420
MPN# 558-420

Everyday Low Price: $56.25

In Stock

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Benefits

Allows Adding 4 Inputs & 1 Output
Works With Holley Terminator EFI
Great For Adding Sensors

Features

High Quality Wiring
Color Coded
Pre-Terminated Pins

What's in the Box

(4) Input Wires
(1) Output Wires

Holley Terminator EFI Input/Output Kit
Add up to 5 extra functions to your Holley Terminator EFI system with this Terminator EFI input/output wiring kit. The base Terminator EFI harness does not include all inputs and outputs prewired, leaving some open for adding extra sensors or functions. This kit contains 5 extra input/output wires, the input wires for Inputs 1-4, and one wire for output 2. These inputs and outputs can perform features and functions that can be programmed via Holley EFI software. Allowable functions that can be wired for inputs for frequency, 0-5V, 0-20V, thermistor, 12V, and ground. While outputs are limited to 12V pulse-width modulation and a +12V switched trigger. Using preterminated pins, easily identifiable wiring colors, and a pinout makes installing them into your existing harness simple.

Holley Warranty - Click Here

Installation Instructions

Download the pdf Link opens in a new window

Holley Terminator X vs Terminator X Max

Published 9/19/25

California Residents:

WARNING: Cancer and Reproductive Harm- www.P65Warnings.ca.gov

About This Brand

Holley, The Heart & Soul of Performance.

For over 100 years Holley has been proven to be an industry leader by providing Mustang enthusiasts and racers with the high performance carburetors , intake manifolds, cylinder heads, and other quality performance components needed for today's competition. Holley's performance Mustang parts are perfect for any daily driven or high horsepower race car.