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:
Wireless remote control/electronic key battery
Replace the battery with a
new one if it is depleted.
As the key may be damaged
if the following procedure is
not performed properly, it is
recommended that key battery
replacement be performed
by your Toyota
dealer.
■If the key battery is depleted
The following symptoms may occur:
The smart ke ...
Fuel information
You must only use unleaded
gasoline.
Select octane rating of 87
(Research Octane Number
91) or higher. Use of
unleaded gasoline with an
octane rating lower than 87
may result in engine knocking.
Persistent knocking
can lead to engine damage.
At minimum, the gasoline you
use should meet the specifi ...
Circuit description
Monitor description
The ecm commands gearshift by turning the shift solenoid valves ”on/off”.
When there is an open or short
circuit in any shift solenoid valve circuit, the ecm detects the problem and the
mil comes on. Illuminating
the mil, the ecm performs the fail–safe and turns ...


