M04 - P4 Harness



Contains all ECU connections from the 6-Way Connector for most engine combinations.

Products that can use this harness

  • Mercury and Mercury2

Click this link to download PDF version of  the M04 – P4 Harness Overview 

M04 – P4 Harness Drawing 


Products that can use this harness

  • Mercury and Mercury2

• This old style Level 1 harness was part of the economy series for Mercury and some people still prefer them today to save on expenses. The harness contains all ECU connections from the 6 Way Connector for most engine combinations.
• This optional harness is used only if Altitude Sensor, Fuel Pressure Sensor or Tuning POT are required. It also has the GP2 output on it.

Design Points to take Notice of.
• The Altitude Sensor and Fuel Pressure Sensor share a shielded wire. Take the shielded part as close to the sensors as possible. They share common earth wires. Solder these connections and insolate them properly. If you use this harness where the sensors is apart you may need to splice in a separate shielded wire for the other sensor. Connect the shields together for interference protection on the spliced section.
• All the input wires are shielded and is 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.

Wire Names and connections on this harness:

POT (Shielded) contains:
• Potentiometer Signal or Wiper (Blue)
• +5V (Red)
• Earth (Black)
Alt/Fuel (Shielded)
• Altitude Sensor (Green)
• Fuel Pressure Sensor (Yellow)
• +5V (Red)
• Earth (Blue)
GP2 Output (Blue/White)
Earth Wire for Screens and sensors (Black)

See the design drawing for thickness and lengths or wires. See the connection drawings in the specific product manual on how to connect the harness to each item it was designed for.

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

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