Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Mil circuit / Circuit description
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

Other materials:
Diagnostic trouble code chart
Hint:
as for the vehicle for mexico, refer to repair manual 2003 corolla (pub. No.
Rm938u).
Parameters listed in the chart may not be exactly the same as your readings due
to the type of instrument
or other factors.
If a malfunction code is displayed during the dtc check in the check mod ...
On–vehicle inspection
1. Inspect cooling system for leaks
Caution:
to avoid the danger of being burned, do not remove the radiator
cap while the engine and radiator are still hot, as fluid
and steam can be blown out under pressure.
fill the radiator with coolant and attach a radiator cap tester.
  ...
Data list/active test
1. Data list
Hint:
using the data list displayed by the hand–held tester or the obd ii scan tool,
you can read the value of
the switches, sensors, actuators and so on without parts removal. Reading the
data list as a first step
of troubleshooting is one method to shorten diagnostic time.
...


