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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    Pre–check
    1. Srs warning light check Turn the ignition switch to the on position and check that the srs warning light lights up. check that the srs warning light goes out after approx. 6 Seconds. Hint: when the ignition switch is at on and the srs warning light remains on or flashes, the ...

    Check short circuit
    If the wire harness is ground shorted as shown in fig. 5, Locate the section by conducting a resistance check with the body ground in step (b). Check the resistance with the body ground.  Disconnect connectors a and c and measure the resistance between terminals 1 and 2 ...

    Inspection procedure
    Hint: hand–held tester only: narrowing down the trouble area is possible by performing ”a/f control” active test (heated oxygen sensor or other trouble areas can be distinguished). Perform active test using hand–held tester (a/f control). Hint: ”a/f control” is the active te ...