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Home >> Subaru >> 2021 >> Crosstrek Hybrid >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 17 (Engine Control System (2.5L) (Diagnostics) (1 Of 4)) >> Diagnostic Procedure With Diagnostic Trouble Code (DTC) >> DTC P0128: Coolant Thermostat (Engine Coolant Temperature Below Thermostat Regulating Temperature) >> General Description >> Diagnostic Method

Diagnostic Method

WARNING: This page is about a different variant/trim than selected.

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

JUDGMENT VALUE SPECIFICATIONS (DIAGNOSIS 1)

Malfunction Criteria Threshold Value
Actual engine coolant temperature Less than 50°C (122°F)
Σ (Estimated engine coolant temperature - actual engine coolant temperature) More than value of Map4
Estimated coolant temperature More than value of Map2
JUDGMENT VALUE SPECIFICATIONS (DIAGNOSIS 2)

Malfunction Criteria Threshold Value
Actual engine coolant temperature Less than value of Map5
Σ (Estimated engine coolant temperature - actual engine coolant temperature) More than value of Map6
Estimated coolant temperature More than value of Map3
JUDGMENT VALUE SPECIFICATIONS (DIAGNOSIS 3)

Malfunction Criteria Threshold Value
Actual engine coolant temperature Less than 50°C (122°F)
TEMPERATURE SPECIFICATIONS - MAP 2

Engine coolant temperature at engine starting (°C (°F)) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Estimated coolant temperature (°C (°F)) 50 (122) 50 (122) 50 (122) 50 (122)
TEMPERATURE SPECIFICATIONS - MAP 3

Engine coolant temperature at engine starting (°C (°F)) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Estimated coolant temperature (°C (°F)) 72 (161.6) 78.9 (174) 78.9 (174) 78.9 (174)
TEMPERATURE SPECIFICATIONS - MAP 4

Engine coolant temperature at engine start (°C (°F)) -7 (19.4) 0 (32) 8 (46.4) 10 (50) 30 (86) 40 (104)
Σ (Estimated engine coolant temperature - actual engine coolant temperature) (°C (°F)) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9)
TEMPERATURE SPECIFICATIONS - MAP 5

Engine coolant temperature at engine starting (°C (°F)) -7 (19.4) 8 (46.4) 10 (50) 25 (77)
Estimated coolant temperature (°C (°F)) 72 (161.6) 78.9 (174) 78.9 (174) 78.9 (174)
TEMPERATURE SPECIFICATIONS - MAP 6

Engine coolant temperature at engine start (°C (°F)) -7 (19.4) 0 (32) 8 (46.4) 10 (50) 30 (86) 35 (95)
Σ (Estimated engine coolant temperature - actual engine coolant temperature) (°C (°F)) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9) 1731.6 (3116.9)

Time needed for diagnosis: 

Diagnosis 1: Less than 1 s

Diagnosis 2: Less than 1 s

Diagnosis 3: 10000 ms

Malfunction indicator light illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.