Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSUBARU1998LEGACY OUTBACK SPORT AWD F4-2.2L SOHCREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTRELAYS AND MODULES - POWERTRAIN MANAGEMENTRELAYS AND MODULES - COMPUTERS AND CONTROL SYSTEMSMAIN RELAY (COMPUTER/FUEL SYSTEM)DESCRIPTION AND OPERATION
1998 Subaru Legacy Outback Sport AWD F4-2.2L SOHC
Main Relay (Computer/Fuel System): Description and Operation
1998 Subaru Legacy Outback Sport AWD F4-2.2L SOHCSECTION Description and Operation
PURPOSE/OPERATION
FUEL PUMP CONTROL RELAY
The Engine Control Module (ECM) receives a signal emitted from the Crankshaft Position Sensor and turns the Fuel Pump Relay "ON" or "OFF" to control Fuel Pump operation. To improve safety, the Fuel Pump will stop if the Engine stalls with the Ignition Switch "ON".
POWER SUPPLY CONTROL RELAY
When the Engine Control Module (ECM) receives an "ON" signal emitted from the Ignition Switch, current flows through the Main Relay. This turns the Ignition Relay "ON" so that power is supplied to the Fuel Injectors, Mass Air Flow Sensor, Idle Air Control Valve, etc..
FUEL PUMP CONTROL RELAY
The Engine Control Module (ECM) receives a signal emitted from the Crankshaft Position Sensor and turns the Fuel Pump Relay "ON" or "OFF" to control Fuel Pump operation. To improve safety, the Fuel Pump will stop if the Engine stalls with the Ignition Switch "ON".
POWER SUPPLY CONTROL RELAY
When the Engine Control Module (ECM) receives an "ON" signal emitted from the Ignition Switch, current flows through the Main Relay. This turns the Ignition Relay "ON" so that power is supplied to the Fuel Injectors, Mass Air Flow Sensor, Idle Air Control Valve, etc..
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.