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Z31 E.F.I Relay and Circuit

EFI Relay location in the Z31 engine bay

The EFI Relay is located behind the battery next to the fusible link box. It is covered by a small plastic flap. The relay controls the power to the fuel injection system, mainly the power to the injectors.

It has four wires connected to it. The diagrams below will explain what these wires do.

*WARNING* - Do this modification at your own risk. We Are not responsable for any issues of your own doing.

EFI Relay Pinout & Wiring Details

EFI relay pin locations Location of the pins on the Relay
EFI relay pin wiring diagram
  1. Red Wire: Goes to ECU pin 6, this controls the relay.
  2. Black with Red Trace: Power in to relay from fusible link. From fusible link, changes to red and then meets up with Pin 114 at the ECU and splits going to each injector.
  3. Black with White Trace: Connects to Pin 35 on the ECU. Also meets up with Green Wire on the Pressure Regulator Control Modulator and the Blue/Red wire on Pressure Regulator Control Solenoid.
    This ends up as a power supply for:
    • Crank Angle Sensor
    • Air Flow Meter
    • Pressure Regulator Control Modulator
    • Pressure Regulator Control Solenoid
    • EGR Control Solenoid
    • Idle Up Solenoid Valve
    • FICD Solenoid Valve
  4. Black with Red Trace: Power in to relay from fusible link. From fusible link changes to Red and then meets up with Pin 114 at the ECU and splits going to each injector.
EFI relay wire color details This diagram describes the wire colors in more detail.

Common Problems

Sources Used