Toyota Corolla (E120): Circuit description

If the ignition switch is turned to the on position, battery positive voltage is applied to the switches, such as terminal ig of the ecu.

Wiring diagram

Inspection procedure

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    On–vehicle inspection
    1. Check cooling fan operation with low temperature (below 83 c (181 f)) Turn the ignition switch on.  check that the cooling fan stops. Hint: if not, check the cooling fan relay and water temperature sensor, and check for separated connector or severed wire between the cooling fan ...

    How to proceed with troubleshooting
    The hand–held tester can be used at step 3, 4, 5, 7, 10. 1 Vehicle brought to workshop 2 Customer problem analysis 3 Connect hand–held tester to dlc3 Hint: if the display indicates a communication fault in the tool, inspect dlc3. 4 Check dtc and freeze frame data Hint: record or pr ...

    Circuit description
    In the diagram below, when the engine is cranked, current flows from terminal st2 of the ignition switch to the starter relay coil and also current flows to terminal sta of the ecm (sta signal). When the sta signal and ne signal are input to the ecm, tr is turned on, current flows to the c ...