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:
Front differential oil seal
Replacement
1. Drain manual transaxle oil
torque: 39.2 Nvm (400 Kgf·cm, 29 ft·lbf)
2. Remove front wheels
3. Remove engine under cover lh
4. Remove engine under cover rh
5. Drain transaxle oil
6. Remove front drive shaft assy lh
sst 09520–01010, 09520–24010 (09520–32040)
7. R ...
Circuit description
If the engine coolant temperature (ect) does not reach 75°c (167°f) despite
sufficient warm – up time has
elapsed.
Dtc no
Dtc detection condition
Trouble area
P0128
Condition (a), (b) and (c):
cold start
after engine is warmed up
& ...
Inspection
1. Thermostat
Hint:
the thermostat is numbered with the valve opening temperature.
Immerse the thermostat in water and gradually heat the
water.
check the valve opening temperature.
Valve opening temperature:
80 to 84 c (176 to 183 f)
Hint:
if the valve opening temperatur ...


