The ECU switches on the fuel pump output when 12V ignition is supplied to the ECU for a period of 2 seconds. The output will then switch off until engine speed is measured by the ECU, it will then turn the output back on again until the engine stops. This is a safety feature as in the event of an accident & the fuel line is cut, once the engine stops, the fuel supply will switch off.

This is switched negative output & must be used to trigger a relay. Our harnesses already have the relays built in.