This J3 auxiliary harness connects to the Dominator EFI J3 ECU connector, giving builders 17 user-programmable inputs and outputs. Note that the J3 connector is also used for drive-by-wire (DBW) applications, so confirm which auxiliary connector your build needs before ordering.
Specifications:
- Connector: J3
- Programmable I/O: 17 user-programmable inputs and outputs
- Harness Type: Auxiliary
- Part Number: 558-403
FAQ
What is the J3 connector used for?
It provides 17 user-programmable inputs and outputs on Dominator EFI, and is also used for drive-by-wire (DBW) applications.
How many programmable I/O does this harness provide?
17 user-programmable inputs and outputs.
Should I order this or the J4 harness (558-404)?
It depends on your build — check whether your application needs drive-by-wire support (J3) versus the 26-I/O J4 connector, and confirm against your Dominator EFI wiring diagram.

