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HOMESERVICE MANUALSSUBARU1998FORESTER BASEREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROLS - BASIC TESTINGECM POWER SUPPLY & GROUND TESTS
1998 Subaru Forester Base

ECM Power Supply & Ground Tests

1998 Subaru Forester BaseSECTION ECM Power Supply & Ground Tests

  1. Check Main Relay

    Turn ignition off. Remove main relay. Connect battery voltage to main relay terminals No. 1 and 2. Check resistance between main relay terminals No. 3 and 5, and terminals No. 4 and 6. See Fig 1. Resistance should be less than 10 ohms in both tests. If resistance is as specified, go to next step. If resistance is not as specified, replace main relay.
    Fig 1: Testing Main Relay
    G98E12058Courtesy of SUBARU OF AMERICA, INC.

  2. Check ECM Power Supply Circuit

    Reconnect main relay. Disconnect ECM harness connector. Turn ignition on. Using DVOM in voltmeter mode, connect DVOM negative lead to ECM harness connector No. 19. In sequence, connect DVOM positive lead to ECM harness connector terminals No. 1, 2 and 39. See Fig 2. Voltage reading on each listed terminal should be greater than 10 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, check and repair circuit between main relay and ECM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.

  3. Check ECM Ground Circuit

    Turn ignition off. Disconnect ECM harness connector. Using DVOM, check resistance between chassis ground and in sequence, ECM harness connector terminals No. 17, 18, 19, 20, 42, 46, 69, 94 and 95. Resistance on each listed terminal should be less than 5 ohms. If resistance is as specified, see IGNITION CONTROL SYSTEM TESTS . If resistance is not as specified, check affected ground circuit between ECM harness connector or check for poor terminal contact in harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.
Fig 2: Identifying ECM Harness Connector Terminals
G98F12059Courtesy of SUBARU OF AMERICA, INC.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
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  • • 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.