Circuit Opening Relay Circuits There are three types of fuel pump control circuits used on Toyota's EFI engines. One type of control, used exclusively with L type injection, utilizes the air flow meter Fc contact to complete the circuit opening relay run winding ground. This is a safety feature which prevents the fuel pump from operating when the engine is not running.
A second type of fuel pump control uses the ECU to control circuit opening relay run winding current. Used on engines equipped with D type EFI and on the 7M-GTE, which uses a Karman vortex air flow meter, this safety feature prevents fuel pump operation whenever the ECU fails to see an Ne (engine rpm) signal. Under these conditions, the ECU removes ground from the circuit opening relay run winding.
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