Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Ecm power source circuit / Circuit description
Toyota Corolla (E120): 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 supplying power to terminal +b of the ecm.
If the ignition switch is turned off, the ecm continues to switch on the efi relay for a maximum of 2 seconds for the initial setting of the isc valve.
Wiring diagram

Other materials:
Inspection procedure
1 Check source voltage
Measure the voltage of the battery.
Ok:
voltage: 10 – 14 v
2 Check air bag sensor assy center
Disconnect the negative (–) terminal cable from the battery, and wait at
least for 90 seconds.
disconnect the connectors from the airbag sensor assy ...
Inspection procedure
1 Inspect dlc3 terminal voltage(tc terminal)
Turn the ignition switch to on.
measure voltage between terminals tc and cg of dlc3.
Ok:
voltage: 10 – 14 v
2 Check harness and connector(dlc3 – body ground)
Check for open and short circuit in harness and connector betw ...
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 ...


