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

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

(1)	Valve	(6)	Rubber packing
(2)	Spring	(7)	Stop ring
(3)	Stopper	(8)	Wax element
(4)	Piston	(9)	Jiggle valve
(5)	Guide

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
Estimated ambient air temperature	≥ −7°C (19.4°F)
Thermostat malfunction diagnosis	Not finished
Engine coolant temperature at engine starting	< 55°C (131°F)
Estimated coolant temperature	≥ 75°C (167°F)
Engine coolant temperature	< 75°C (167°F)
(Estimated − measured) coolant temperature	> 20°C (68°F)

Time Needed for Diagnosis: 30 seconds

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
Estimated ambient air temperature	≥ −7°C (19.4°F)
Thermostat malfunction diagnosis	Not finished
Engine coolant temperature at engine starting	< 55°C (131°F)
Engine coolant temperature	≥ 75°C (167°F)
(Estimated − measured) coolant temperature	≤ 20°C (68°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)