The MFI relay (automatic shut down relay) supplies battery voltage to the fuel injectors, electronic ignition coil, generator, and the heating elements in the oxygen sensors.
The PCM controls the relay by switching the ground path for the solenoid side of the relay on and off. The PCM turns the ground path off when the ignition switch is in the Off position. When the ignition switch is in the On or Crank position, the PCM monitors the crankshaft_position_sensor and camshaft_position_sensor signals to determine engine speed and ignition timing (coil dwell). If the PCM does not receive the crankshaft position sensor and camshaft position sensor signals when the ignition switch is in the Run position, it will de-energize the MFI relay.
Along with the fuel pump relay, the MFI relay attaches to a bracket on the drivers side of the dash panel.
Last modified on 2008-11-11 17:39:11