Main Relay (Computer/Fuel System): Description and Operation

Control Relay Location:

PURPOSE
The control relay supplies positive current to the EGR and purge solenoids, air flow sensor, ECM, and injectors.

NOTE: Failure of the control relay will interrupt power supply to the fuel pump, injectors and/or the ECM, resulting in start failure.

LOCATION
The control relay is located in the right kick panel.

Control Relay:

OPERATION
Ignition switch in the START position:
1. Current flows from the ignition switch through the control relay coil C2 to ground.
2. This turns on control relay switch S2, supplying battery voltage to the fuel pump.

Ignition switch in the ON position (engine RUNNING):
1. The ECM supplies the ground circuit to the control relay coil C3, keeping control relay switch S2 closed, energizing the fuel pump.
2. Battery voltage is also supplied to the ECM so that the ECM detects the power supply to the fuel pump.
3. When the ECM detects this power supply (switch S2 closed), it supplies the ground circuit to control relay coil C1.
4. This closes the control relay switch S1, supplying power to the ECM and various other components (injectors, relays and sensors).

Ignition switch in the ON position (engine STALLED):
1. The ECM interrupts the ground supply to control relay C1, opening control relay switch S2.
2. This turns the fuel pump OFF.