Toyota Corolla (E120): Circuit description
If the engine coolant temperature (ect) does not reach 75°c (167°f) despite sufficient warm – up time has elapsed.
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Dtc no |
Dtc detection condition |
Trouble area |
| P0128 | Condition (a), (b) and (c):
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Monitor description
The ecm estimates the engine coolant temperature (ect) based on starting temperature, engine loads, and engine speeds. The ecm then compares the estimated ect with the actual ect. When the estimated ect reaches 75 c (167 f) the ecm checks the actual ect. If the actual ect is less than 75 c (167 f), the ecm will interpret this as a fault in the thermostat or engine cooling system or thermostat and set a dtc.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Component operating range
Monitor result (mode 06 data)
Refer to page 05–27 for the detailed information on checking monitor status.
Other materials:
Fail–safe chart
If any of the following codes is recorded, the ecm enters the fail–safe mode.
Check for intermittent problems
Hand–held tester only:
by putting the vehicle’s ecm in the check mode, the 1 trip detection logic is
possible instead of the
2 trip detection logic, and the sensitivity to de ...
Inspection procedure
1 Check operation(stop lamp swtich assy)
Check that the stop light comes on when the brake pedal is depressed,
and turns off when the brake
pedal is released.
2 Input signal check
See input signal check on page 05–745.
check the indicator light when the brake pedal ...
Monitor description
The battery supplies electricity to the ecm even when the ignition switch is
off. This electricity allows the
ecm store data such as dtc history, freeze frame data, fuel trim values, and
other data. If the battery voltage
falls below a minimum level, the ecm will conclude that there is a fault ...