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Engine Control System (Diagnostics - Introduction): General Description: Caution

  1. Airbag system wiring harness is routed near the ECM, main relay and fuel pump relay.
    CAUTION:
    • Do not use electrical test equipment on the airbag system circuits.
    • Be careful not to damage the airbag system wiring harness when servicing the ECM, TCM, main relay and fuel pump relay.
  2. Never connect the battery in reverse polarity. Doing so will damage the ECM instantly, and other parts will also be damaged.
  3. Do not disconnect the battery cables while the engine is running. A large counter electromotive force will be generated in the generator, and this voltage may damage electronic parts such as ECM etc.
  4. After connecting the battery terminals, wait for at least 10 seconds before tuning the ignition switch to ON. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
  5. When disconnecting the connectors of the electrical components, always be sure to turn the ignition switch to OFF. Perform the Clear Memory after connecting the connectors. Ref. to COMMON (diag)>CLEAR MEMORY .
  6. When measuring the voltage or resistance of individual sensors or all electrical control modules, use a tapered pin with a diameter of 0.6 mm (0.024 in) or less and touch it to the tip of terminal.
    G13866148Courtesy of SUBARU OF AMERICA, INC.

    Never insert the tapered pin into the terminal because it deforms inside which may lead to a malfunction.

    G13866149Courtesy of SUBARU OF AMERICA, INC.
    CAUTION: When replacing the ECM, be careful not to use the ECM of wrong specification to avoid any damage on the fuel injection system.
    NOTE: When replacing the ECM of the models with immobilizer, immobilizer system must be registered. For detailed operation procedure, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER".
  7. Take care not to allow water to get into the connectors when servicing or washing the vehicle in rainy weather. Avoid exposure to water even if the connectors are waterproof.
  8. Use the body ground terminal for the grounding point when measuring voltage and resistance inside the passenger compartment.
    G13866150Courtesy of SUBARU OF AMERICA, INC.
  9. Use the engine ground terminal or engine assembly for the grounding point when measuring the voltage and resistance in engine compartment.
    G13866151Courtesy of SUBARU OF AMERICA, INC.
  10. All parts related to the engine control system are precision parts. Do not drop or otherwise apply impact. Do not reuse the parts that are dropped accidentally.
  11. Observe the following cautions when installing a radio in vehicle.
    CAUTION:
    • The antenna must be kept as far apart as possible from the ECM. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Electrical Component Location>LOCATION>ENGINE UNIT .
    • The antenna feeder must be placed as far apart as possible from the ECM and engine control system harness.
    • Carefully adjust the antenna for correct matching.
    • When mounting a large power type radio, pay special attention to the three items mentioned above.
    • Incorrect installation of the radio may affect the operation of ECM.
  12. When disconnecting the fuel tube, release the fuel pressure. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel>PROCEDURE>RELEASING OF FUEL PRESSURE .
  13. Warning lights may illuminate when performing driving test with jacked-up or lifted-up condition, but this is not a system malfunction. The reason for this is the rotating speed difference between the front and rear wheels. When engine control system diagnosis is finished, perform the VDC memory clearance procedure of self-diagnosis function. Ref. to COMMON (diag)>CLEAR MEMORY .
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