EFI Main Relay & EFI No. 2 Relay (Supra Turbo)

The EFI No. 1 fuse (30-amp) supplies constant battery voltage to EFI main relay. The EFI main relay is turned on by M-REL terminal of Engine Control Module (ECM). When EFI main relay is turned on, voltage is supplied to EFI No. 2 relay, +B terminal of ECM, data link connector No. 1 and various other electrical components. EFI No. 1 fuse, EFI main relay and EFI No. 2 relay are located in fuse/relay box at driver's side front corner of engine compartment, near the battery.

EFI No. 2 fuse (30-amp) supplies constant battery voltage to EFI No. 2 relay. When EFI No. 2 relay is energized by voltage supplied from EFI main relay, relay closes and voltage is provided to +B terminal on fuel pump Electronic Control Unit (ECU). Fuel pump ECU is located in driver's side rear corner of trunk. See Fig 1. Fuel pump operating speed is controlled by the operating condition of the engine such as: starting, light load or heavy load. The ECM delivers an input signal from FPC terminal on ECM to FPC terminal on fuel pump ECU in accordance with the engine operating condition. The fuel pump ECU uses this input signal to determine how much voltage should be delivered to the fuel pump for varying fuel pump operating speed.

Fig 1: Locating Typical Fuel Pump ECU (Supra)

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