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Home >> Hyundai >> 2015 >> Sonata Eco >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 125 (Engine Control System Diagnosis (1 Of 2) (HEV)) >> DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) >> General Information >> DTC Detecting Condition

General Information: DTC Detecting Condition

WARNING: This page is about a different variant/trim than selected.
Item Detecting Condition Possible Cause
DTC Strategy
  • Coolant temperature not reached warm up state
  1. Faulty cooling system
  2. Faulty ECT sensor
  3. Poor connection or damaged harness
Enable Conditions
  • Fuel-cut off phase <20%
  • Low load phase < 50%
  • 11V < Battery voltage < 16V
  • Intake air temperature decrease compared to Start Intake air temperature > -10°C(-14°F)
  • -10°C(14°F) < Coolant temperature at start < 54.4°C(131°F)
  • -10°C(14°F) < Intake air temperature at start
  • No high engine speed(4800rpm) with vehicle stopped
  • No relevant failure
  • Ambient temperature > -10°C(-14°F)
  • Percentage of high vehicle speed phase (Vehicle speed > 87 mph) < 90%
Threshold Value
  • Measured coolant temperature < 74°C(165°F) When modeled coolant temperature > 85°C(185°F)
Diagnostic Time
  • 10~30 min. depending on coolant temperature at start and driving pattern
MIL On Condition
  • 2 Driving Cycles