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    Sale!

    Holley J1 A/B I/O Auxiliary Harness, For Dominator, HP & Terminator X | 558-400

    Vendor: Holley EFI
    Part Number: 558-400
    Save $17
    Sale Price $135.95 Regular Price $152.95

    Available to order. In-stock orders typically ship in 1 to 2 business days.

    Not sure it fits your vehicle?
    Email sales@berryperformancesales.com with your year, make, model and engine, and we'll help you check fitment before you order.
    Fast Fulfillment: In-stock orders typically ship within 1 to 2 business days.
    Free Shipping on Orders Over $99 | Excludes freight shipments
    International Shipping Available: email sales@berryperformancesales.com for a quote.
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    This auxiliary harness connects to the 8-pin Metri-Pack input/output connector found on most Holley EFI main harnesses, providing four dedicated input wires and four dedicated output wires for Dominator, HP EFI, Terminator X, and Terminator X Max systems.

    Specifications:

    • Connector: J1 A/B, 8-pin Metri-Pack
    • 4 input wires, 4 output wires
    • Assorted wire colors for easy identification
    • Compatible With: Dominator, HP EFI, Terminator X, Terminator X Max
    • Part Number: 558-400

    Note: the Terminator X main harness includes a 3-pin input/output connector rather than the 8-pin connector this harness is designed for.

    FAQ

    What Holley EFI systems does the 558-400 harness work with?

    Dominator, HP EFI, Terminator X, and Terminator X Max.

    How many inputs and outputs does it provide?

    Four input wires and four output wires through an 8-pin Metri-Pack connector.

    Does this fit the Terminator X harness the same way?

    The Terminator X main harness uses a 3-pin input/output connector, which differs from the 8-pin connector this harness connects to on other systems.

    Shipping Policy
    • Free shipping on orders over $99 (excludes freight shipments).
    • In-stock orders typically ship within 1 to 2 business days. Weekend and holiday orders are processed the next business day.
    • Orders ship from Defiance, Ohio and a nationwide network of warehouses and manufacturers.
    • Items showing an ETA are not in stock yet. ETAs come from the manufacturer and can change.
    • No P.O. Boxes. International orders need a shipping quote, so email us first.

    Read the full Shipping Policy

    Return Policy
    • 30-day return window from the ship date. Returns must be approved first; email sales@berryperformancesales.com with your order number.
    • Items must be unused, complete and in the original packaging.
    • A 20% restocking fee applies, and return shipping is paid by the buyer.
    • Not returnable: installed or modified parts, opened or used programmers and tuners, custom orders, Open Box, and Clearance or Final Sale items.
    • Damaged, defective or incorrect items must be reported within 48 hours of delivery with photos.

    Read the full Return Policy

    Disclaimer

    All products are sold for off-road use only unless otherwise specified. Buyer assumes all responsibility for installation and operation. Seller is not liable for any incidental, indirect, or consequential damages — including engine failure, labor costs, or vehicle downtime — resulting from the use of any product sold.

    By making a purchase from Berry Performance Sales, you acknowledge and agree to abide by the terms and conditions of these Policies.

    For any questions or concerns, please contact us — we’re always happy to help.

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