Part 5: Wiring Block Diagram

Basic Circuits

Block Diagram


The Block Diagram shows the basic connection paths used for successful operation. The arrows indicate the primary direction of the control or communication. It is important to consider the Engine & ECU Wiring harness complete with all associated sensors as a complete single unit. While some parts of the Engine & ECU Wiring Harness may need to be adapted to suit your vehicle configuration the overall harness should not be varied greatly. For details of individual sensor wiring refer to the electronic version of the Ford Focus Wiring Diagrams.

The OEM Engine Control Unit is designed to be located within the engine bay and only needs to be mounted with the connectors protected from direct water ingress.

Part 3: Donor Vehicle Connector Locations

Connector Locations

Due to the modular design of the Ford Focus wiring loom there are only a small number of connectors and components critical to independent engine operation.


Located in in the main engine bay fuse box this is the link between the engine specific wiring and the power supply, fuses and relays to control engine ancillary devices.

C90 C200 & C809

C200 – Located on the drivers side, below the steering column.

C809 – Located on the back of the instrument cluster.


C391 & C456