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:

Inspection procedure
Hint: start the inspection from step 1 in case of using the handheld tester and start from step 2 in case of not using the handheld tester. 1 Read value of handheld tester(front speed sensor) Select the datalist mode on the handheld tester.  check that there is no difference betw ...

Inspection procedure
1 Check side squib(lh) circuit(airbag sensor assy center front seat airbag assy lh) Disconnect the negative () terminal cable from the battery, and wait at least for 90 seconds.  disconnect the connectors between the airbag sensor assy center and the front seat airbag assy (lh ...

Skid control sensor
Replacement Hint: replace the rh side by the same procedure as the lh side. 1. Remove rear wheel 2. Remove rear brake drum subassy 3. Disconnect skid control sensor wire Disconnect the skid control sensor wire connector from the skid control sensor. 4. Remove rear axle hub & ...

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