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:
Overhaul
Hint: components:
1. Drain manual transaxle oil (m/t transaxle)
torque: 39.2 Nvm (400 Kgf·cm, 29 ft·lbf)
2. Drain automatic transaxle fluid (a/t transaxle)
torque: 17.5 Nvm (178 Kgf·cm, 13 ft·lbf)
3. Remove front wheel
4. Remove engine under cover lh
5. Remove front axle hub lh nut
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Circuit description
The shift solenoid valve sl is turned ”on” and ”off” by signals from the ecm
in order to control the hydraulic
pressure operation, the lock–up relay valve, which then the controls operation
of the lock–up clutch.
Fail safe function:
if the ecm detects a malfunction, it turns the ...
On–vehicle inspection
1. Inspect speedometer
check the operation.
Using a speedometer tester, inspect the speedometer fro allowable
indication error and check
the operation of the odometer.
Reference:
Notice:
tire wear and tire over or under inflation will increase the indication error.
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