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DTC P0128 COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE)

DTC P0128 COOLANT THERMOSTAT (COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE)

OUTLINE OF DIAGNOSIS

Detect the malfunction of thermostat function. Judge NG when the engine coolant temperature is lower than the estimated engine coolant temperature and the difference between them is large. Judge OK when the engine coolant temperature becomes 70°C (158°F) and the difference is small before judging NG.

COMPONENT DESCRIPTION


(1)

Valve

(4)

Piston

(7)

Stop ring

(2)

Spring

(5)

Guide

(8)

Wax element

(3)

Stopper

(6)

Rubber packing

(9)

Jiggle valve



ENABLE CONDITION

Secondary Parameters Enable Conditions
None



GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

DIAGNOSTIC METHOD

Abnormality Judgment

Judge NG when the continuous time of completing the malfunction criteria below becomes more than 30 seconds.

Judgment Value

Malfunction Criteria Threshold Value
Battery voltage

≥ 10.9 V

Engine coolant temperature at engine starting

< 55°C (131°F)

Engine coolant temperature

< 70°C (158°F)

(Estimated − measured) coolant temperature

> 30°C (86°F)

Vehicle speed

≥ 30 km/h (19 MPH)

Estimated engine coolant temperature

≥ 70°C (158°F)

Estimated ambient temperature

≥ −7°C (19°F)



Time Needed for Diagnosis: Not fixed.

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

Normality Judgment

Judge OK and clear the NG when the malfunction criteria below are completed.

Judgment Value

Malfunction Criteria Threshold Value
Battery voltage

≥ 10.9 V

Engine coolant temperature at engine starting

< 55°C (131°F)

Engine coolant temperature

≥ 70°C (158°F)

(Estimated − measured) coolant temperature

≤ 30°C (86°F)



DTC CLEAR CONDITION


When the OK idling cycle was completed 40 times in a row

When “Clear Memory” was performed


MALFUNCTION INDICATOR LIGHT CLEAR CONDITION


When the OK driving cycle was completed 3 times in a row

When “Clear Memory” was performed


FAIL SAFE

None

ECM OPERATING AT DTC SETTING


Memorize the freeze frame data. (For test mode $02)

Memorize the diagnostic value and trouble standard value. (For test mode $06)