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.

