Toyota Celica 2005 Repair Manual page 310

2 Check cooling system.
CHECK:
Check that there is a defect in the cooling system which causes over cool, such as abnormal radiator fan
operation, modified cooling system and so on.
OK
3 Check thermostat (See page CO−10).
YES
Replace ECM (See page SF−78).
2005 CELICA (RM1131U)
DIAGNOSTICS − ENGINE (1ZZ−FE)
NG Repair or replace cooling system.
NG Replace thermostat.
309
DI−111