Circuit Description

The ignition relay, also called the EFI relay, provides ignition positive voltage to the control module and other engine control components anytime the ignition is ON. One side of the coil of the EFI relay is always grounded. The other side of the coil receives 12 volts from the powertrain control module (PCM). When the coil is energized, a magnetic field closes the switch side of the relay, supplying power to the following engine components:

• The fuel pump relay, also called the circuit opening relay
• The heated oxygen sensors (HO2S)
• The mass air flow (MAF) sensor
• The evaporative emission (EVAP) control system solenoids and vacuum pump
• The idle air control (IAC) valve
• The PCM