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Home >> Subaru >> 2013 >> Legacy Premium, Automatic CVT Trans >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Diagnostic Trouble Code (DTC) Detecting Criteria (H4DO) >> Diagnostic Trouble Code (DTC) Detecting Criteria >> DTC P0128 Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature) >> Diagnostic Method

Diagnostic Method

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

JUDGMENT VALUE

Malfunction Criteria Threshold Value
When any one of the followings is established.
< Judgment 1 >
Actual engine coolant temperature < Value of Map 4
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) > Value of Map 5
< Judgment 2 >
Actual engine coolant temperature < Regulated temperature - Value of Map 6
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) > Value of Map 7
< Judgment 3 >
Estimated engine coolant temperature - actual engine coolant temperature > Value of Map 8
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) > Value of Map 9
MAP 4

Estimate ambient temperature °C (°F) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Threshold Value °C (°F) 70 (158) 70 (158) 70 (158) 70 (158)
MAP 5

Engine coolant temperature at engine starting °C (°F) -7 (19.4) 0 (32) 8 (46.4) 10 (50) 30 (86) 40 (104)
Threshold Value °C (°F) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1200 (2160)
MAP 6

Estimate ambient temperature °C (°F) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Threshold Value °C (°F) 17.9 (32.2) 11.1 (20) 11.1 (20) 11.1 (20)
MAP 7

Engine coolant temperature at engine starting °C (°F) -7 (19.4) 0 (32) 8 (46.4) 10 (50) 30 (86) 35 (95)
Threshold Value °C (°F) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1500 (2700)
MAP 8

Estimate ambient temperature °C (°F) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Threshold Value °C (°F) 11.1 (20) 11.1 (20) 11.1 (20) 11.1 (20)
MAP 9

Engine coolant temperature at engine starting °C (°F) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Threshold Value °C (°F) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9)

Time Needed for Diagnosis:  300 - 700 seconds

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

Judge as OK and clear the NG if the continuous time while the following conditions are established is more than the predetermined time.

JUDGMENT VALUE

Malfunction Criteria Threshold Value
All of the following conditions are established.
< Judgment 1 >
Actual engine coolant temperature ≥ Value of Map 4
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) ≤ Value of Map 5
< Judgment 2 >
Actual engine coolant temperature ≥ Regulated temperature - Value of Map 6
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) ≤ Value of Map 7
< Judgment 3 >
Estimated engine coolant temperature - actual engine coolant temperature ≤ Value of Map 8
and  
Σ (Estimated engine coolant temperature - actual engine coolant temperature) ≤ Value of Map 9
and  
Actual engine coolant temperature ≥ Regulated temperature - Value of Map 10
MAP 10

Estimate ambient temperature °C (°F) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Threshold Value °C (°F) 17.9 (27.7) 11.1 (20) 11.1 (20) 11.1 (20)

Time Needed for Diagnosis:  300 - 700 seconds