Circuit Description

The circuit opening relay provides ignition positive voltage to the fuel pump. The circuit opening relay is controlled by the powertrain control module (PCM) and receives ignition positive voltage from the EFI relay. The PCM monitors the crank signal circuit for voltage when the ignition switch is in the START (engine cranking) position. When the crank signal circuit indicates the engine is cranking the PCM energizes the circuit opening relay. The PCM also energizes the circuit opening relay whenever reference pulses from the crankcase position (CKP) sensor circuit are detected. If the crank signal circuit does NOT indicate the engine is cranking the PCM will energize the circuit opening relay based only upon reference pulses.