MEXO2 - 2 Mercury2 ECU Harness



Complete Harness pack including wires and relays.

No engine connectors.

Products that can use this harness

  • Mercury2

Download the PDF of the MEX02 – 2 Harness Overview 

MEX02 – 2 Harness Drawing Description

MEX02- 2 Harness Drawing 


Products that can use this harness

  • Mercury2


  • This new style Level 2 harness was developed for Mercury2 to save install time and minimize fault-finding afterwards. The harness contains all ECU connections from all of the Connectors and will serve most engine combinations.
  • It is the recommended Wire and Play loom that has all the relays and fuses pre-wired in the loom. No need for extra power wires etc. It is designed to contain all the ECU connection wires so that all connection options on any engine are possible. The manual is also based on this harness structure for wire colours and placement.

Design Points to take Notice of.

  • It comes with PVC sleeving, heat shrink and a roll of cloth tape to dress up upon final installation. You will still need the connectors of the engine as this is a universal harness. It is not Plug and Play. Note that other items like Sensors, Stepper Idle Controller, Coil Igniter Modules etc. are still add-ons and has to be connected or wired in according to the manual drawings and recommendations.
  • It does come with a Water and Air sensor option built into the harness. The water sensor is a Lug that is bolted onto the thermostat housing and the Air sensor is a button sensor without housing that could be mounted inside the air cleaner box. In most cases, they are cut off and the harness connected to the actual engine’s water and air sensor.
  • This harness comes with 3 Mechanical relays that are wired according to ECU requirements. Relay 1 is the clean power relay and must not be used for coils, Injectors or inductive loads. Each Relay has an Inline Fuse for protection of that segment. For large applications, you may still add external fuse boxes for more individual circuit protection.
  • Injector and Coil looms are also available to ease installation. They are sold separately because of different connection options between straight and V engines.
  • All the input wires are shielded and are earthed on the ECU side with the small black lead that must be connected to the ECU earth. Never connect a shield on the engine or chassis of the car.
  • Crank and Cam sensor wires are enclosed in one shield. They share common power and earth wires. If you use this harness where the sensors are apart you may need to splice in a separate shielded wire for the other sensors. Connect the shields together for interference protection on the spliced section.

Wire Names and connections on this harness:

Crank (Shielded) contains:

  • Crank Sensor (Green)
  • Cam Home Sensor (Yellow)
  • Cam1 Sensor (Red)
  • Cam2 Sensor (Blue)
  • +12V Ignition (White)
  • Earth (Black)

Map (Shielded)

  • Map Sensor (Blue)
  • +5V (Red)
  • Earth (Black)

TPS (Shielded)

  • TPS Sensor (Blue)
  • +5V (Red)
  • Earth (Black)

WAT (Shielded)

  • Water Temperature Sensor (Red)
  • Earth (Blue)

AIR (Shielded)

  • Air Temperature Sensor (Red)
  • Earth (Blue)

Lambda (Shielded)

  • Lambda Sensor (Red) (Shield)
  • Lambda Sensor Earth (Blue) (Shield)
  • Lambda Element Earth (Black)
  • Lambda Element Power (Red)

Alt/Fuel (Shielded)

  • Altitude Sensor (Green)
  • Fuel Pressure Sensor (Yellow)
  • +5V (Red)
  • Earth (Blue)

POT (Shielded) contains:

  • Potentiometer Signal or Wiper (Blue)
  • +5V (Red)
  • Earth (Black)

POS (Sleeved) contains:

  • 8x Positive outputs (Various Colours)
  • +12V Relay Power (Red)
  • Earth (Black)

NEG (Sleeved) contains:

  • 8x Negative outputs (Various Colours)
  • +12V Relay Power (Red)

GPO (Sleeved) contains:

  • 2x Negative outputs (Various Colours)

Fuel Pump (Red)

Ignition Power (Orange)

RPM Output signal for TCU or other systems (Green)

TPS Output signal for TCU or other systems (Yellow)

BAT+ 3xRed

Earth Wire for Screens and sensors (Black)

3x Relay Sets of wires (12)

See the design drawing for thickness and lengths or wires.

NB! Wires that are not connected must be isolated to prevent shorts or interference.

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