Toyota Corolla (E120): Circuit description

The ignition switch provides circuit power and the ecm provides the circuit ground that illuminates the mil.

Mil operation is checked visually: it should be illuminated when the ignition is first turned on. If the mil is off all of the time or on all of the time, use the procedure below to troubleshoot it. The mil is used to indicate the ecm’s detection of a vehicle malfunction.

Follow this procedure using the hand–held tester or an obd ii scan tool to determine the cause of the problem and to check the mil.

Wiring diagram

Inspection procedure

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    Circuit description
    When the ignition switch is turned on, battery positive voltage is applied to the coilwhich closes the contacts of the efi main relay (marked: efi) and supplies power to terminal +b of the ecm. This signal causes current to flow to the coil, closing the contacts of the efi relay and supplyin ...

    Overhaul
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    Inspection procedure
    Hint: read freeze frame data using the hand-held tester or the obd ii scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the ...