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Home >> Subaru >> 2006 >> Legacy GT spec.B >> Repair and Diagnosis (Single Page) >> Engine Performance >> Testing & Diagnosis >> Diagnostic Trouble Code (DTC) Detecting Criteria (H4DOTC) >> Diagnostic Trouble Code (DTC) Detecting Criteria >> DTC P0128 Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature) >> Diagnostic Method

Diagnostic Method

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

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value
Battery voltage ≥ 10.9 V
Estimate ambient temperature ≥ -7°C (19.4°F)
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) Engine coolant temperature > 30°C (54°F)
Vehicle speed ≥ 30km/h(19MPH)

Time Needed for Diagnosis:  30 seconds

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

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

Judgment Value 

JUDGMENT VALUE

Malfunction Criteria Threshold Value
Battery voltage ≥ 10.9 V
Estimate ambient temperature ≥ -7°C (19.4°F)
Thermostat malfunction diagnosis Incomplete
Engine coolant temperature at engine starting < 55°C (131°F)
Engine coolant temperature ≥ 75°C (167°F)
(Estimated - Measured) Engine coolant temperature ≤ 30°C (54°F)