Toyota Tacoma manuals

Toyota Corolla Repair Manual: Circuit description

If the engine coolant temperature (ect) does not reach 75c (167f) despite sufficient warm up time has elapsed.

Dtc no

Dtc detection condition

Trouble area

P0128 Condition (a), (b) and (c):
  1.  cold start
  2.  after engine is warmed up
  3.  engine coolant temperature is less than 75c (167f)
  • Thermostat
  • cooling system
  • engine coolant temperature sensor
  • ecm

Monitor description

The ecm estimates the engine coolant temperature (ect) based on starting

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 enabling conditions

Typical malfunction thresholds

Typical malfunction thresholds

Component operating range

Component operating range

Monitor result (mode 06 data)

Monitor result (mode 06 data)

Refer to page 0527 for the detailed information on checking monitor status.

Refer to page 0527 for the detailed information on checking monitor status.

Coolant thermostat (coolant temperature below thermostat regulating temperature)
Dtc p0128 coolant thermostat (coolant temperature below thermostat regulating temperature) Hint: this is the purpose of the thermostat malfunction detection. ...

Inspection procedure
Hint: read freeze frame data using the hand-held tester or the obd ii scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is usefu ...

Other materials:

Hydraulic test
1. Perform hydraulic test Measure the line pressure. Notice: Do the test at normal operation atf temperature 50 to 80 c (122 to 176 f). The line pressure test should always be carried out in pairs. One technician should observe the conditions of wheels or wheel stopper outside ...

Power point socket assy rr
Replacement Hint: components: 1. Remove parking brake hole cover subassy 2. Remove floor shift shift lever knob subassy (m/t transaxle) 3. Remove console panel upper 4. Remove console box carpet 5. Remove console box subassy rear (m/t transaxle) 6. Remove console box subassy rear (a/t tr ...

Inspection procedure
Hint: read freeze frame data using the hand-held tester or the obd ii scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the ...

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